I like the 22/45 because the grip angle and controls are very similar to my 1911. I tend to like [and shoot] pistols with this grip angle better than the Mark II/Mark III with it's Luger angle. Glocks also feel 'wrong' to me due to grip angle.
If you don't shoot, think about your future gun purchases. Do you plan on a 1911? If so, the 22/45 will help you get some of the controls down in muscle memory, and the angle is similar.
What about those with 1911-esque shapes, a la HK USP? Same as above.
Try both in your hands and pick the one that you feel you can bring onto target best and hold on target best.
For ME that was the 22/45.
As far a performance, I believe the only significant difference between the two is the grip angle.
Buckmarks have a good rep. Try the
Rimfire Central forum for more rimfire-specific info!