Bring up a discussion on which objective lens sizes are best and you'll get a catfight going. All sorts of opinions are out there on what's best, and I don't think anyone has presented the perfect argument for his or her position. So... I think that your logic of going for the low mount 50mm objective is well thought out, and that you should do that.
It's a Leupold, so there's a 99.9% or better chance that it'll never give you trouble. And if it does, Leupold will fix it for free. And 50 years from now, when your great grandson drops in on a big rock or hammers nails with it, it'll still get fixed for free. That's one of those things that other companies can equal, but never beat.