I've got several Carsons- Med. M-4, Small M-4, Four C20's, Large M-16, Small M-16, Small M-21, LDC-8, Large M-18, BAK, and M-18 Flipper
My favorite carry piece is a Med. M-4, luckily the C2O's are essentially Med 4 framelocks. My favorite is has a drop point Stellite blade, bolsters and OD micarta handle scales. My fav C20 would be a classic clip point in 6K.
I think my favorite overall Carson is the M-18. I love the beefy handle and BIG blade. Mine has a stonewashed S30V blade w/ top swedge, Ti bolsters and green micarta scales. Just the cat's pajamas!
Get a Med. 4, you won't be dissapointed.