If you're really going to off road it, and have nice fenders/bumpers- extended bump stops
It kind of depends how wide the tire is, and how the rim fits. Stock tires are 29", so 30 isn't much taller. If it's on an 8 inch wide custom wheel that half sticks out of the fenders, then the extended stops come into play because you've got to clear the fender lips.
If it's on a stock rim and the tires aren't very wide, probably don't need the extended stops. They'll tuck up into the fenders and clear the lip
My tires are 30x9 on stock wheels with a 2 inch BB and they look kind of lost in the wheelwells. Go for 31s.
good luck with the project