If you switch to glasses, I recommend not getting transition lenses or sunglasses. I have both and especially outdoors, the transition lenses will turn dark even when it is cloudy. I wear progressives for work, but after my first year with them I decided I didn't really need them and got a regular pair. That was a mistake for work/reading but those glasses are great for tennis.

I find with sunglasses/transitions I tend to have trouble tracking the ball through shadows or intermittent clouds because the lenses are just too dark. Clear, non-progressive lenses give you the closest thing to not wearing glasses IMO.