I guess I'm a little late the party on this post, but I thought I'd add my .02$.
I was trying to decide between those exact 2 guns last summer. Fortunately, I ended up being able to fire both of them before purchasing. Unfortunately, that didn't help my decision process.
In the end I chose the 22/45 mkiii. What decided it for me, was that accuracy and longevity were more important than aesthetics and cool factor. Let's face it, the SR-22 looks better. I still want one and if I find another for a good price, I wouldn't hesitate.
I love my 22/45 though. And the takedown IS painful the 1st few times, now its a breeze. That should definitely not be the deciding factor for you though.
Now it's just a matter of finding some ammo. Good luck with the decision.....unless it's already happened. Then good luck finding ammo