i prefer dig. no matter what im driving. if i lose, or cant handle it, i upgrade and practice so that i CAN launch correctly, and setup the car so it will launch properly with traction.
roll definately seems less conspicuous to some people, but i sure hope people arent setting up roll or dig races in front of the public (besides chosen spectatorship at certain local 'tracks')
of course, you can usually tell what someone will prefer by the location/time of day/ and what car they are driving. rwd's and awd's like to go from digs it seems, unless its a supra or some turbo car with like 1500rpm of powerband

fwd's like rolls as well it seems, esp hondas and other various cars with "high rpm/valve timing technology like vtec, vvtl-i, etc). turbo fwd's - dont bother asking a dig.
but dont forget - the skyrine! can do it both ways and win...every time!

(as i typed this as a joke, i actually remember that newer skylines can be setup to convert from awd/rwd with the flip of a switch

)