Which is Crueler?

Whoa, man. Yeah, releasing an indoor cat into the wild, where it has to fend for itself is entirely more humane than giving them a quick shot for a peaceful eternal slumber.

Certain death vs a chance at living a healthy normal rest of their lives as strays. Considering both cats came from outdoors anyhow, the latter is the lesser cruelty to me, were I willing to forgo any responsibility for their futures.

I guess I'll share my opinion since I've owned several cats which we've had declawed.

Just to clarify - I've had a tom declawed before. He hobbled around miserably on bloody bandages for a week and never forgave us. He went from being lovable and cuddly to being a surly biter and learned to punch rather than claw. He eventually began to insist on being let outside, and became an indoor/outdoor cat for several years, hunting effectively if differently. He could even tree climb to some degree.