I have 2 pairs of MJ's and a pair of costas.
The one thing I'll say is that in terms of polarization and ability to see in water, glass lenses are awesome compared to any type of plastic. Light through plastic changes the polarization direction, and differently depending on the stress in the plastic, so the polarization efficiency ends up a bit blotchy. Glass lenses have superior polarization, regardless of brand.
MJ, Costa, and Smith are to my knowledge the only ones that still make glass lenses. But all 3 also make plastic lenses, which IMO aren't all that significantly better than the billion other companies which make plastic lenses. There are a million types of plastic, the index is different, which brings some differences in the prescription world but not a ton of difference for non rx. If gonna spend the dime on a premium label like that, make sure its glass. If you don't wanna spend that much, cool, get plastic but feel free to step down to an intermediate brand then. So long as its got a scratch coating and an anti reflective coating, but can get that in mid range stuff.
After that its all about color and light transmission. Costas in particular tend to be really dark at 10 or 12% vlt, great for offshore stuff and beach, not great for the forests of PA. 14-18% is good for big stream work. I like 20+% for forested small stream stuff, which gets you to low light lenses, like MJ's Maui HT and Smith really does well with their igniter stuff. Personally I like amber colors for the contrast, straight gray is neutral in that regard. Note that a lot of lenses are mirrored, so they look to be a different base color than they actually are.
