First World Problems. They plague us all, the decision most got on my heels at this current moment in time is that of the Nike+ Fuelband vs the Jawbone Up. Both are similarly priced items, both with iOS apps, both tracking activities. Therefore when is comes to choosing between the two, the choice is hard.
The Nike+ Fuelband has distinct advantages over the Up, it syncs wirelessly over Bluetooth and has a screen showing what the time is and other things that you might want to know. It is put on the wrist by detaching the sides and then reattaching them when worn. This allows a tight fit however seems to be quite a bit harder than the Up however will stay on with a tighter fit. This makes it more suited for jumping around and running where the device is more likely to fall off.
The screen on the Nike+ Fuelband is quite useful for those interested at the current moment for looking at the footsteps and the time. This makes it more suited to those regularly exercising and therefore means that it should be referred to often, whereas the Up seems to be quite discreet, only needing a gentle push of the button from time to time to change the mode. This makes it more suited to the kind of person interested in looking at their activity from time to time and not needing instant updates. The screen also makes the Nike+ Fuleband quite larger and not as discreet.
The two devices are very different in their users. The Fuelband is for someone interested in knowing how well they are exercising and how far they have run whereas an Up user would be interested in leaving what they do all the time, shown by the fact that it tracks sleep as well. Therefore the choosing of your device depends on your lifestyle.