What they said, but you can go with a compromise optic in a variable power 1-4x scope, turned to 1 power they are supposed to be -almost- as fast as an RDS, and you can tune them up to 4x to get some magnification. To get magnification out of an RDS you need a magnifier which is bulky. Downside to the 1-4x variable is that you have to worry about eye position and eye relief with a scope while you generally don't have to with an RDS.
The 1-4x variable option has been graining popularity among the tactical crowd and, from what i understand, rules the 3-gun circuit.
I see some of the guys that shoot in matches at my range use red dot scopes on their pistols. I took a couple shots with one and it was easy to shoot with. Thought about getting one as I get older the sights on my pistols seem to be getting harder to see.