I'm not a huge fan of either, but in principle I prefer a system with clear tiers and a higher level of differentiation, so I guess Trophies appeal to me a bit more.
I'd like the ability to turn of the notification though - I hate playing an immersive game and having a notification pop up, it's just so silly. For example in Dead Space you're getting into the vibe of feeling alone and threatened, you make a frantic kill, then get told 'woo hoo, you've just killed your xth foe'. It just breaks the spell of SP titles for me. I don't mind in MP, but in SP I want a way to switch off in game notifications.
Sorry, rant over!
Try to be reasonable... its easier than you think...