Depends on what type of gamer/player you are.
Get M32 if you want to kill a zombie in about 4/5 hits (Based on a 250HP zombie)
Get a Claymore if you wanna be sneaky and that shit. But IT CANNOT kill a zombie in one fucking hit. (Based on a 250HP zombie)
OR get BOTH, zombie comes near, plant claymore, blow it a few yards away whip out your m32 and boom, You got a nice manwich.
and if getting gp is a problem just use the claymore and go into Elim Pro