Paintball and simunitions? For tactics, use of cover,etc... in my opinion both are similar. However, when it comes to weapon handling it's simunitions hands down. Not even a second thought...not even close. With simunitions, I am able to use an exact copy of the weapon I carry on duty (Glock 17). There are two versions of the glock simmunition guns...one is a conversion, the other is made by glock and will only ever fire simmunition rounds. The polymer portion of this gun is blue. The other gun we use is the MP5 with the conversion kit
(now we're having fun!) Anyway, these act exactly like our duty weapons, same magazines, same # of rounds, same problems associated with a gun fight (reloading, stoppages) and we can use and draw from our holsters just like in real life. Plus they can be used anywhere in any scenario. Building searches, traffic stops, suspicious persons. And for civilians..carjackings, robberies, home invasion. Your training with simmunitions is only limited by the number of scenarios your imagination can come up with.
So, between FATS, AIS, paintball or simmunitions, there is no question as to which provides the most realism. If you can find a place to use them, you won't be disapointed.
If not you, then who?