It really just depends. If you're into bombing and jumping, I'd go 158 for either. If you're more into playing around and jibbing, I'd go with 154 Proto.
I'm the opposite of most guys. When torn between two sizes, I'll generally lean toward the larger. Then again, I don't do much jibbing and you won't see me hucking any crazy spins either. For me, the added stability of the larger size favors my style of riding which is a lot of hard charging and jumps.