Well, a cleansuit is a single-piece garment. MOPP gear is modular. It would be more akin to the firefighter’s turnout gear than it would be to a NBC suit or something like that. As to whether or not most zombie soldiers should be wearing them, I was under the impression that the Cataclysm struck all at once, with very little time to anticipate what was happening. The blob raised the dead, the triffids sprouted, the mycus invaded, creatures from hell or the nightmare dimension attacked, and everything was complete and utter chaos. Most of the military personnel operating in FEMA camps and the like would probably be Guardies activated at the last minute for a desperate attempt at damage control, wouldn’t really expect them to be kitted out perfectly. The ones from crashed helicopters would likely be in the same predicament, since they wouldn’t have been geared up before landing unless they were dispatched as QRF. Lab soldiers would be hit-or-miss on full kit, depending on whether or not they died while on-shift, so to speak, or while resting peacefully in the barracks.
Either way, more gear is always cool.