Ability to feel pain is somewhat tricky to determine, as we can't measure it from the outside. I'm inclined to think that insects, trees and bacteria all have some kind of 'conscious experience', but the contents of their experience must be a lot different to ours. For sure, trees don't have plans, thoughts nor emotions the way we do. But they might have some other kind of sensations of 'light' or 'goodgoing' or whatever we simply fail to imagine due to limitations of our brains =)

Ah, but meat tasting delicious - that is a point of view that didn't come to my mind. Enough spices and some oil, and anything tastes delicious, so for me it is mostly about making sure to get enough protein etc. In which case fish is a safe choice. (I think the scientific research suggests that fish feel pain, too.)