I can hit fairly well with either SPAA. I find the M16 to be much more effective vs. jabos than the Osti, but the Osti is pretty much required vs. buffs. All you'll get vs. buffs in an M16 is 1-3 assists in most cases.
A very important consideration for picking the right SPAA is stealth. If the jabo herd spots you, you're gonna be dead fairly quickly regardless of what you're driving, assuming the nme's serious about their attack. IMHO it's MUCH better to be in an unspotted M16 than a spotted Osti because the extra armor does you no real good when the rain of 1000# bombs comes down. So, picking the right SPAA should depend in part on the color of the map's terrain tiles in the AO and the GV skins on the map. You want the SPAA that blends in the best.
Of course, DO NOT USE TRACERS. Otherwise, the paintscheme doesn't matter a bit.