The MarkIII has the thumb mag release as opposed to the heel release, has a LCI (loaded chamber indicator), a magazine disconnect, and a mechanism to lock the gun with a key. I personally like the thumb mag release, but the heel release isn't that bad. A MKII and a MKIII should shoot equally as well. A bit of a warning when it comes to the MKII and MKIII pistols, field stripping for the first time is really really really really going to suck. Have someone at the range show you how, or check out some sites online for instruction. Great pistols overall, I've had a few and they all shot groups about the size of a loonie at 30 yards with bulk ammo.