I play hard/perma death, granted I have played... quite a few fire emblem games, don't know how many cause the GBA ones kinda blend together. At the very least 3, probably more.
I don't find hard to be that much bad, however yeah the reinforcements are annoying, almost requiring you go through levels with them more than once. I am used to fire emblem being that way though, so I might be biased.
I'd say hard/perma death is the best way to play, but that's for me. From replies here, it sounds like normal is the best for new players.