I have a fitbit one and really like it. I sync it with myfitnesspal and endomondo. I think it overestimates calorie burn, at least for me. But I love that it counts both steps, flights of stairs, miles, and active minutes. You can have friends on it and see how you compare to them, too. I just clip it on the center of my bra and go. Oh, and it can track your sleep, too.
Good luck deciding!
Lost the first 100 with Medifast, now working on the last 25