You can see this as a pro or a con, but the Garmin Vivofit calculates step goals for you. This is great for someone who isn't going to hit the recommended 10k steps a day right off the bat. It gradually increases your goal for the day, based on how you have been doing. I find this awesome because it encourages you to improve, no matter what level you are at, but I do miss the vibration and party of the Fitbit when you hit 10k steps. It would be nice if these trackers allowed you to set your own goal, but Garmin is onto something with this proposed goal thing.
The cons include that the Vivofit, didn't work as well when running with the jogging stroller because my arm wasn't moving as much. With the Fitbit, it didn't seem to matter if I ran with or without the jogger, but again, the Fitbit does overestimate steps a bit. The other major con is really that the Garmin Connect app just isn’t as cool as the Fitbit app. That is the bottom line. And maybe most of your friends are Fitbit wearers and not on Connect. There are a few programs that sync activities from Garmin Connect to the Fitbit app, but they only sync activities, not total steps. So, you can choose watch vs. friends list or you can wear a Fitbit Zip to have your bells and whistles dashboard that you like and your friends list but wear the Vivofit as your watch and wrist-worn accelerometer.
I think the verdict is still out on whether I like the Vivofit over the Charge. I prefer the Vivofit as a wearable. The waterproof feature and year-long battery are major, major pluses for me, and I like having all my workouts in one place, so on the Connect webpage I see my triathlon workouts and my Vivofit steps. But Fitbit works with my jogging stroller and estimates stairs (although often widely inaccurate in doing so, it's nice having that extra motivation).
Both Garmin and Fitbit also sync with MyFitnessPal, by the way, which is awesome, if you use that app. Fitbit may lend to you eating more calories than you should. I definitely lost weight exercising less but eating better with my Garmin, since it only transferred over "active calories" (calories burned during an activity) and not all those 18k steps I did throughout the day that weren't as active. But Fitbit makes you feel better about yourself haha. Such a tough call!
The Skinny: the best multisport, activity-tracker watch on the market; maybe it doesn't matter if you don't like the app because your watch is so awesome...but you still might miss your Fitbit dashboard.
One last plug for Garmin. The Vivoactive would be my solution to the issues with accuracy in the Vivofit, since this is a GPS watch. It's the do-it-all watch comparable to the Fitbit Surge (but better, in my book). For the running, stepping, cycling, and swimming enthusiast, this watch does it all! You can download golf courses to it and do all the stuff that those golf GPS gadgets do, but this is on your watch. It can count your strokes in the pool and your laps and all that fun stuff. It does GPS for running, so here you have your GPS watch. For cycling, it does everything a tri watch will do, especially if you add the cadence sensor to your bike. So, yes, it is pretty amazing, and it’s sleek and cool looking. However, the battery life is not for an Ironman athlete, at least not for an age-grouper like me, since it only lasts 10 hours in GPS-mode. Oh well. Still pretty awesome! This is the watch I would want if it wasn't half the cost of the 920XT. For the money, I'd rather just use my Fitbit of Vivofit for day-to-day use and then spend the extra dollars on getting my high-end Ironman watch. But I'm a little nuts. For most folks, the Vivoactive is the watch to buy! Will let you know if I try it out.
Diaz, KM, et al. Fitbit: An accurate and reliable device for wireless physical activity tracking. Int J. Cardiol. 2015 Mar 4;185:138-140.