MarkB
Legend
What, time travel?
No, travel through serious time distortions. River says as much, as I recall - it's better at getting through 'traffic' - so the dirt bike / SUV comparison is an apt one, though I'd suggest that the time bracelet is more closely analogous to a bicycle.
The only aspect of time travel the bracelet has been shown to do better is slipping through time distortions, and to some extent that makes sense - smaller object, less easy to get caught up in things. The fact that it can handle one single, specialised aspect of time travel better than the TARDIS is no reason to assume that it does a better job in general.