Snape!!! <3

So Snape! Sure Regulus had to die to destroy the locket but it was fast and could only happen once. Snape was with Voldemort, the greatest evil wizard like ever, quite a bit. He had to lie to him, sneak around, not show he was allied with anyone else, try and get to Harry when Voldemort didn't want him to go. Snape had to risk so much, almost everyday!!

Persephone16 is so right, Regulus died quick. Severus has years of the mental agony and stress. Then add having Harry thrown in his face (memory of torment from James and love for Lily) The mental toll had to be devastating. This could have contributed to his low weight and signs of poor health. Nerves and mental anguish.

Absolutely.

Snape had nothing to live for. He lost Lily and he never got the DADA job. Regulus hadn't even lived for a fair amount of time when he chose an instant death for the greater good. (NOT a DH hint)

Both, but Snape more.

Both, but I find Snape's sacrifices a bit touching.

Snape risked more and for much longer