I'm mostly concerned about mount compatibility. I plan on buying the M5S with no mount and putting it on a Bobro mount with no spacers, I want it as low as possible since it will be going on a Beretta ARX-100. So if that won't work out I would like to know.

Also, is there any reason at all that makes the M5 better than the M5S?

I'm in the same boat, and are all the T1 mounts compatible with the S?? Plus I haven't seen anybody stock an M5s without the factory mount.

This thread was helpful. > https://www.ar15.com/forums/AR-15/Mount-for-aimpoint-m5s/18-746217/

thanks Cliff

Both are really great red dots maybe the best at the moment but I went with the M5s because of the obvious lower battery compartment. It however does present a mount problem as most manufacturers aren’t making specific mounts for the M5s. I like 1.93 mounts myself and found that if you add .45 to any mount that you’re looking at you will get a close overall height. So for instance I went with a Scalarworks absolute co witness at 1.42 giving me an overall height of 1.87 when adding .45, which is extremely close to my normal setups of 1.93. So close that it’s not even perceivable to my eye or head position.

Now it gets tricky if you are really trying to get that perfect absolute co or lower 1/3 co. So unfortunately the M5s is a bit of a trial and error optic. A great optic but a bit of a bastard to be honest.

Makes it easy to go with a T2