Ugh. Just started the game and I can't decide whether to keep on playing on Casual or start over on Classic. On Classic I'd probably just start over everytime I lose a unit anyway. "Lost" a few units early before I understood the mechanics of weaknesses (I didn't take the warning about archers against pegasus seriously enough!), the weapon triangle etc, but I feel a bit dirty for having completed the a couple of maps with losses that don't matter afterwards.
Might just do Casual on first run, seems like a game I'd like to replay anyway.
I had the debate in my head as well. I just stuck with casual on my 1st and only playthrough. It's my first fire emblem so I didn't want to get super frustrated and plus there is a game over if chrom or your created dude does so I figured it was an ok compromise. I have a lot of games to play so I didn't feel like having to restart after every person gets hit weird or ganged Up on. I'm still really enjoying it.