Ruger
We have both a Buck Mark (wife's gun) and a Mk. II. (my gun) The Mk. II is the same as the Mk. III except for smaller details.
So far, the Mk. II is more reliable than the Buck Mark. Sometimes, the Buck Mark doesn't strip a round off one of the magazines. I squeeze the trigger and all I get is a *click*. This is annoying, since Kate wanted to use it for her home defense gun. We haven't gone as far as to mark magazines numbers on them. But they are both factory new magazines.
The Buck Mark (Contour model) has a more comfortable stock grip than the Mk. III, and a bit softer recoil. But the instructions don't say how to field strip it for a proper cleaning. One has to go to youtube or something for that. Also, it requires tools to do. The gun is very accurate.
The Mk. III is going to be harder to get apart initially; the receiver is a very tight fit to the frame, and requires a mallet to tap it off. This makes some people very nervous, then they go around saying how it should just be cleaned with Gun Scrubber or brake cleaner. The triggers are about equal. The Mk. III has the sight as part of the elegant tubular receiver, which is integral with the barrel. On the Buck Mark, it is part of the top rail, which is a separate part, and gets removed each time the gun is field stripped. My Mk. II is about 20 years old now, and even though the receiver is a loose fit to the frame, it is still deadly accurate, since the receiver/sight is integral with the barrel. Ruger factory magazines are cheaper than Browning's. The Mk. III is more comfortable than the 22/45, IMO. The 22/45 may have the grip angle of a 1911, but its grip is very thin and it just feels like there's something missing, IMO.
Having had both, my vote's for the Ruger.