Burby looks more menacing, and its more of a sexy face. Zeppy looks menacing but in a unplanned way, and he also looks like he doesn't know whats going on.
zeppy? Burby..you look like a fuckin gangster. I swear you look you're about to pop a fuckin' cap in my ass.. And Mark...well mark looks like he's gunna try to ninja chop my head off...
Burby is like the evil overlord who has people exectured who look at him wrong. Zeppy is like the guy who slaps you on the ass.