[Hessah]

the M.Def from SPR MIGHT benefit you if you're pvping against a mage... but generally monsters wise, not that many mob does M.Dmg over all, and SP can always be easily replenished with stones...

So yeah as lvra said, the crit bonus is the key focus here... though STR doesnt give any other benefit so I guess SPR gives a LITTLE bit more minor benefits... (provided that the dmg from Crit is more or less equal to the dmg from STR...)