I have a model 48 that was factory fitted w/a 22lr cylinder it shoots just about the same as my 17-3 and my 617, it was my only 22 revolver for a long time so it has seen a lot more long rifle than magnum rounds.

I would go with conventional wisdom get a 48 or 648 and have a long rifle cylinder fitted if you want a convertible. Also you see 48's with both cylinders for sale now and then(not cheap).