I’ve been looking for the best tracker for my dog (Charlie, a 4yo lab rescue) for a while now, and finally decided to pull the trigger recently on 3 of the top options out there and compare them against each other to see which I would stick with.I bought the Whistle, Tractive and the Fi, and put them all on the same collar (lucky Charlie!) to make sure I was testing them under the exact same conditions.We kept them all on the collar for 2 weeks and looked for a couple of things when testing:GPS Location AccuracyTime Taken to Alert an EscapeBattery LifeCollar / App ExperienceGPS Location AccuracyWe live in a pretty rural area, so when we’re out and about walking Charlie - cell service can be spotty. We also rarely see anybody else on our walks, so Charlie is off leash most of the time.He’s also a rescue, and although we got him when he was very young and have trained with him a lot, he does occasionally still follow his nose when he gets excited!Because of this, location accuracy was very important to us. And honestly, we didn’t have very high expectations here because of where we live, but we were pleasantly surprised. They all tracked our walks well both on and off leash (fi and whistle particularly, the tractive seemed to lose signal more frequently) and gave us enough confidence that they could do it when we needed them too.Time Taken to Alert an EscapeAfter doing research into dog trackers, I learned that how quickly they send you an alert after your dog gets out of your house can differ greatly between products - and is a very important metric if you have an escape artist for a pup.We set up a fake ‘escape’ scenario in our house, and had my wife take Charlie out on a walk (without her phone on her or anything) and we would see how long it would take to get a notification that he had ‘got out’. We tested this twice on two different days for increased accuracy and I had my stopwatch ready for accurate measuring.Results are below in order of speed:Fi - 1m52s & 2m07s (!)Tractive - 3m35s & 4m02sWhistle - 5m12s & 5m28sBattery LifeIn short, this is how long each device lasted for us on a full charge:Tractive: 3 daysWhistle: 5 daysFi: 18 daysClear winner here again. We’ve been told to expect worse battery life than most since we live pretty far out, but 18 days is just crazy.Collar & App ExperienceHonestly I wasn’t expecting to have this as a section when I first ordered these products, but there were some really cool features that the Fi and Whistle had that I thought was worth talking about, so here we are. (The tractive didn’t offer these so haven’t talked about them here)The Whistle focuses on health, and claims it can track anything from licks to scratches, and it digests these to give you a daily wellness score for your pup. We found it interesting to see and track these, but also noticed that they weren’t always very accurate, so felt we couldn’t rely on it for an accurate representation. But fun to have nonetheless.Fi’s app experience was the most robust, and offered everything from sleep tracking to local rankings. And the rankings feature was BY FAR our favorite. They basically show you where your dog’s step total (from their activity) ranks compared to other dogs of the same breed using Fi (so you know whether they should be taking more or less for their age!), or compared to other dogs nearby, in your town and your state. We had no idea they had this feature and thought it was so cool that we found ourselves checking Charlie’s rank every day…and don’t know if we could ever go without checking again haha.Overall, after putting the trackers through their paces I would rank them:1. Fi2. Whistle3. TractiveHonestly, I expected them all to be quite similar in their abilities and what they offered, but in the end the escape alerts, battery life and app experience of the Fi was far and away better than the other too. Although we returned our Whistle, it was the next closest, and we found that the Tractive was quite a way behind when it came to performance in the end (also returned it).This collar really does track through GPS, but the phone app has software bugs and GPS reception is weak, and my experience was that the GPS locations were updated only about every 5 minutes -- dogs can cover alot of distance in that time. Also annoying is the slick marketing and deceptive product info, confusing documentation. You really only find out the true capabilities and complications of the system when you completely read the through the documentation and understand it on the phone app (no printed documentation provided), which costs you the price of a subscription ($99). Prior to that, they make you think the using collar is the easiest thing you've ever done. If you have the patience to tolerate the poor tech support (only by email within daytime hours), and learn the quirks -- this collar system could actually locate your dog in an emergency. But the quirks don't give you a sense of reliability, some of which are: app reports erroneous locations even though dog is at home, map showing GPS location plots only works some of the time, you get erroneous text location messages when dog is in fact at home, and worst of all -- GPS reception is weak with infrequent location updates.Up until not long ago, I absolutely loved this product. I was actually what you could call a cheerleader for them.With that said, there are pitfalls that you will have zero, or very, very little ability to foresee from the company's online documentation and description. These issues are extremely ambiguous and very minimally stated by Fi online, so much so that the odds of you seeing same are slim to none.The first issue is that if your device craps out, there is no prorated refund of the service fee. If it's month to month that's not a big issue, but yearly or multi yearly, it's a significant one because you lose it all even if it worked only one day. That SHOULD HAVE BEEN well and clearly stated in multiple places, but it's hidden and worded so as to be essentially not stated at all. I was clipped on both of my latest subs, one with about a month left and the other about 11 months....gone.Another potentially problematic issue is the collar. The module attaches to the collar by small "swivel lugs". It's hard to explain their workings here, but know that they have a significant chance of breakage if pressure is applied to the band. Two of mine broke, one from my Malinois getting her collar caught on a low strand of barbed wire for literally a couple of seconds, the other from attaching a leash to the collar to walk her, andtwo friends of mine had the same issue (from then on I always used a separate collar for that). Once these lugs are cracked or broke, it's over as far as conventional utilization goes, and you will have to find another way to attach it to some other strap collar, as there's no way to use the expensive Fi collar for it, as it will then be in two unconnectable pieces (the module serves as a "link" in the collar, and if you can't utilize it you will have a 2 piece connectable collar).Another potential issue is that if you don't utilize WiFi as a static "home" area, you are SOL if the module has issues, no matter what the issue is....even if it simply "breaks" or fails due to any other issues. It works perfectly fine using only your smartphone (and redundant backup features), but if at any time something goes wrong with your module, they are going to tell you it's due to not utilizing that feature no matter how long you successfully used it otherwise. One of mine worked fine for almost a year then crapped out to the point of not even being able to power up at all, and not using that limited WiFi was all of a sudden ostensibly to blame despite months of successful use otherwise. Using the WiFi is of course better for battery life by hibernating until an escape, but since I'm literally right by my dog for about 98% of the day there's no difference at all for me.If you lose a collar in anything not wholly open like a field, and instead lose it in brush, etc., you are likely SOL as the location WILL bounce around. It'll get you fairly close....but often 100 or more yards away.I surely hate having to switch from Fi, but after years of pretty successful use, I'm now seeing issues I simply failed to foresee until I was hit by them, and they are no small issues.The price of Fi far exceeds most of their competition. Merely replacing a proprietary collar is over $30, and it's absolutely useless if there's no module there to link the pieces together...so, it's useless as a simple collar absent the module. The one advantage to switching now is that I see how much other brands have dropped in price relative to Fi. I bought all of mine from Fi, utilizing coupons for up to $70 off, yet there are other systems that are still below the cost of Fi systems.My big regret is having pointed so many friends and family to Fi, but that was prior to my knowing about these issues.There are good things about Fi, to say the least, the topmost being EXTREMELY friendly and quick customer service. They, of course, don't make company policy. They alone DO, however, absolutely rate five stars in and of themselves, which works out the 2 stars I'm compelled to give here only due to how good they are...they are the sole reason I don't rate the product as low as possible. Considering that I have one wholly failed module, one lost collar-module system, and I still have to pay out the year subscription fees anyway, customer service staff are again the SOLE reason that I give Fi 2 stars.