I prefer the Ruger MK II over the MK III. No loaded chamber indicator, no mag disconnect, and the heal mag release works fine. I don't see the need for a push button on a .22 target pistol. It isn't really any faster once you get used to the heal release.
I agree with this. Although I have a MKIII 5.5 bull myself, its only because it was my first handgun and so it has sentimental value to me. I had a nice approx 7 in barrel heavy taper barrel MKII which was a great gun. To some degree I should have kept it, but whats done is done. The side mag release really doesn't matter for target shooting. Also the loaded chamber indicator is more for people who aren't safe at the beginning. I never accident with a gun without that feature.
To the OP - maybe the best answer since there are so many options, is to be patient and wait for a great deal. I got this Hamden high standard trophy from the mid 70s for under $400. It takes some patience, but good deals are out there.