in this fantasy world, can i be invincible? if so, then jumps for sure. Nothing like hucking yourself off a giant table.
otherwise, i'd take rails. you can learn so many new tricks without fucking yourself up, and if rails includes urban than rails for sure.
just saying this because i have had 5 injuries on jumps (including shinbang (and yes its an injury)), and only 1 on rails (sprained wrist).