I bought M&B early during the beta and played it disturbingly much, but I've never tried Warband. I'm always suspicious about adding firearms to a mostly melee-based game. Like how PVK is ruined. People who don't see it as a problem always present the "Well yeah but if you get close to them, they're dead!"-argument. There's the "if" in that sentence, meaning there's a propability of you dying before you even have a chance of fighting back. Dying to something like that, even if your team wins the battle in the end, doesn't make for good and fun gameplay.
Then again, they already did two games with no guns, so I guess it's okay if they make one with them, even if it happens to suck.