i'd say HC if it weren't for the fact that medics have an absolutely horrid time trying to do their jobs as effectively in it, if they themselves had a single hud that displayed downed teammates, that'd be ok with me long as it didn't show anything else.
Also, gotta agree with whoever said tagging is a major part of the game, i've recon tagged people flanking and gotten spot assists time after time that way and saved ~6-7 people in the process.
Regular is annoying with the whole "oh hi, i'm a sniper, i'm gonna tank 7-10 shots while i tip-toe around your bomb planting C4." Everything else is tolerable i suppose...
I'll probably be going hardcore once i get all the weapons/gadgets/etc.. figured out how i like them.