I started with glass lids, and had all of the problems mentioned... algae growth, salt creep, and etched glass which at least every couple of years necessitated replacement of the glass.
Then I ditched the glass and used eggcrate instead. When I did that, I expected to see a change in pH due to better gas exchange. I saw an average rise of just 0.1, based upon a year of numbers before and after the change.
I always felt like the eggcrate was less than ideal in terms of light transparency (not to mention aesthetics), so after a few more years I had custom polycarbonate-framed mesh lids made by Artfully Acrylic. I think they are still sponsors here. For what they were, I thought the price for the lids was high, but I've been using them for 5 years and they are still in great shape and look awesome.
In my climate, the issue with mesh lids (or no lids) is evaporation and indoor humidity. It's not a problem during summer when the A/C runs a lot or during spring and fall when the windows are open, but in winter it's a big issue. I have a commercial dehumidifier running right now, and it's removing about 6 gallons of water a day, reducing the humidity from 80% to 50%. Without the dehumidifier, I would be having problems with mold/mildew, wet windows, and who knows what else. I'm seriously considering going back to glass lids for the winter months. And I should point out that dehumidifiers are power-hungry beasts. They will make a noticeable difference in the electric bill.
With a skimmer running and an open sump, gas exchange is not an issue, IME, and glass lids do not reduce gas exchange in any significant way.
I don't like saying the usual reefing folklore if there's data.
