What optic would you recommend for a SP5 9mm? Thinking a RMR. Any others to consider?

I guess it depends on your engagement distance. I am partial to Aimpoint's. I like the Patrol optic for your platform.

RMR's are excellent as is the Holosun for a bit less money. RMR is the most rugged and after watching Sage Dynamics I feel the Holosun is a very close second

Love aimpoints but feel the patrol optic is too big. Love them on ars though. Wanted a lighter more compact optic. 9mm maybe 100 yards but realistically 50 yards and under. No experience with RMR but know trijicon makes good things. Thanks

I prefer a closed emitter RDS when possible, over an open emitter design. Easy to put lens covers on a closed design, or wipe them when needed. Not always easy to get water/debris out of an open emitter. For example, shooting in the rain. Just takes one drop of water to block that emitter and the red dot will not show up.

Good point.

I'm partial to the irons. They are really quick and intuitive once you replace the castle sight with the correct diopter sight. You just might be surprised how well it works.

If you must go red dot, the Trigicon MRO would be my choice.

Aimpoint Micro.

Will any of the sights co witness with the diopter? I'm looking at a BT low profile mount?