dual beretta's would be retarded though. there's no point to it. too much noise, too little accuracy. sure, you'll look badass, but you'll get killed when the hordes come to the sounds of the gunfire.
a zombie wouldn't go down with anything but a complete brain destruction. filling their bodies w/ bullets ain't gonna do much except slow them down. thus, you need accuracy. thus, any single pistol would be better than any other akimbo setup.