I've done it both ways. I ended up mostly using an Rx mask. The contacts worked, and I can wear them fine, but my eyes are such that if I wear contacts, I need reading glasses to read menus and such. I read small print perfectly with no correction. And I can read gauges just fine with single-vision masks. So it was just simpler to use the Rx mask. I can get to my glasses okay without having to walk around in the mask. And it's good to wear the mask while you're in the water, anyway.
I personally also found that with a mask I have a greater tolerance for variations from my actual precise distance diopter than I would be comfortable with in glasses, so the diopter steps in the off-the-shelf lenses was no problem. So as long as I get close, the mask is good. I have both Tusa Rx lenses for one Tusa mask and a cheap Rx mask from Amazon, the ones that commonly go by the Promate brand. I see no real difference between them, and I can't imagine that for me there would be any real improvement with custom lenses. I do keep contact lenses around, though, and I use them more often for surface activities, like kayaking, where dealing with spray (or falling in) is a nuisance and because my variable tint glasses just can't get Ray-Ban dark.
But my choice is strictly a convenience thing for someone who wears trifocals topside. Contacts are cheap enough.
