I went from contacts with clear glasses to prescription transitions oakleys. TBH, I could never ride without glasses over my contacts anyway - I just found that my eyes/contacts dried out - so there are no real disadvantages in comparison, and the transitions lenses are fine. Based on my research people generally find a brown tint beat for riding. It's what I have and it works.
Just be aware of a few things about them. They don't work in the car - they will stay clear as there is no UV. For this reason, I'd go for a design that looks alright with clear lenses. My Oakley Scalpels look daft and that's an understatement. Nice to be able to wear them in the pub/cafe or whatever too. If you ride in very bright conditions (chance would be nice as I live in Scotland) then be aware that they can take a minute or so to lose their tint. So, if you go from bright open hillside to dark woods then they can struggle to keep up. I've never had a problem with this in practice. Perhaps in the alps. Depending on your prescription you can be quite limited on choice of frame with many simply being an insert behind a non prescription lense. This is because Sunglasses generally have a bigger curve to the front of the frame which makes them unsuitable for higher prescriptions (it distorts the vision). I'm +3 in one eye which is beyond Oakley range. I found an optition that would make this to order claiming special techniques which would get round this. Not so. Stick to manufacturer specs on limits. Mine are bearable, but they are only .5 beyond what Oakley do.
I have health insurance through work so I get glasses essentially for free up to a yearly limit, but otherwise mine were around 320 which for me is pretty steep.
Sorry for poor spelling...I'm on my phone with large fingers.
Hope that helps.