A strong OG is absolutely easier to find than a strong Center. There is zero doubt in my mind on that one.I'm not so sure they're easier to find than centers.
You can get either well into every draft. But there are more good OGs than there are good Centers, and many good OTs who have short arms move inside on top of that. It's not even close.
And again I'm not saying the Rams are going to do that. I just wish they would.