Polarized lenses
I can't comment on their approval by the FAA, but after several hundred hours behind a pair, I can confirm that there is no problem reading digital displays, except at the odd gas pump. When that happens, I just tilt my head about 30 degrees and the readout becomes as clear as a bell. Never had a problem with a GPS or anything else, though I'm sure manufacturers could provide genuine data on their displays if that's a concern for you. As for rainbow perspex, you do get a bit of that (stress lines in the material) but not a great deal and it's certainly not a significant distraction.
The benefits of lower glare, lower eye strain, and easier spotting of other aircraft far outweigh any deficiencies, real or perceived, in my mind. I'll never fly with anything else again.