most android phones are hackable/rootable/romable/etc ...
i used to have an od, then i got a d2g. i wanted something different/bigger than these so i studied both the dx and tb. when handling both, features-wise, asthetics-wise, etc. i chose the dx over the tb. cost difference wasn't much of a factor for me, because i know if i buy the cheaper device and not happy with it, then i would likely want to buy the device i'm going to be happy with on the first try to cut my losses down the road.
the dx is more popular, easily has more accessories, better screen aspect ratio, etc. the tb has a 4G radio, but 4G is not yet available i many areas. i asked at a vzw store nearby, they told me 4G won't hit this area until about 1 year. also the tb is not an entirely new design device, it's just got updated hardware/internals inside a standard/pretty much the same shell.
either way, the dx appealed to me more than the tb.