I usually reload,unless it's someone I'd want dead or really don't care much about (I remember Viconia thwapping Keldorn right after I obtained Carsomyr and I went "Meh, didn't like that git anyway").
Usually I do sort of get attached to my party members, at least if they're properly fleshed out. I mean, really, Minsc dies. You wouldn't reload...? I thought so
Being able to ressurrect dead party members is rather nice, for me it often created the challenge of completing fights without anyone dying (or, even worse when sticking to BG series references: getting Imprisoned). But if I don't ressurrect them they should stay dead, none of that KotOR-style nonsense where they cheerfully get up again after battle.
Wizard. I always start out as one (if they're an option). How long I'll stick with him depends on how well they're done though. In BG2 I didn't really play anything but a Wizard, in Skyrim I didn't last very long as pure caster on the other hand.