"Best" depends very much on the objects physical traits, the distances you need to measure and the precision you want/need. There's no sensor that's all round best (well, perhaps a pro LASER scanner, but it's too expensive to be a serious contender in hobby robotics).
The Sharp distance sensors goes up to 5.5m.
(Sharp Comparison Sheet
of different rangers (IR and US) doesn't list the above mentioned Sharp sensor and US can be used at a larger range than what's mentioned, but it's informative none the less.
It doesn't mention LASER rangers either (Like used by eg. Bushnells) - rangers, not scanners - which is yet another way to shave that goat, but I think that you'd have to hack a device containing such a beast, as I haven't seen any sold as just the ranger unit alone.
A LASER ranger will obviously be the most precise and able to measure the distance to what's covered by the small LASER dot and at a much larger range - Tank LASERs work on at least up to a few miles (I should have gotten some when the Russian Army had their large "closing sale" way back - seriously high powered IR LASERS, around 40W IIRC - I could have gotten all the cats in the 'hood... In one shot
Electronic measuring tapes using a LASER are expensive but works A+.
In comparison, the US measuring tapes are just bareable on a good day, if you have a large bare wall in an empty room, don't need too high a precision (i.e. a bit better than eyeballing it) and don't breathe too heavy, but in a furnished room... Pure Monte Carlo (at least that goes for the units I own and others I have tried).
In summation: Select your sensor after your targets size, shape and range