Glass lids, IMHO, are better reserved for terrariums, cages where humidity is important. On a marine aquarium, they reduce gas exchange, and are constantly in need of cleaning. Letting them build up salt crust, or even water droplets will reduce light on a reef. Plastic lids are pretty much the same thing... Housing escape artists would be the only reason I'd have one on a marine aquarium, say, if you were keeping a big eel, or an octopus. Something that would be likely to destroy a mesh lid. They do cut down on evaporation, which can be a good thing, or not... depending on how your system runs.
Mesh lids work well for most reefs. Keep fish from jumping (and yes, virtually ALL fish can jump!) I've even seen smaller fish jump THROUGH 1/2" eggcrate. Lights generally pass right through, with little or no deflection. They'll evaporate quite a bit more, but as I said, that can be a good thing. I run Kalkwasser... you can't add more than your tank evaporates every day. I'm not currently, but I've even been known to put a fan on the tank surface, intended to increase evaporation.
Artfully Acrylic, among others, make a very nice looking screen top, if a bit pricey. They don't really work any better than a DIY or kit screen top, but they sure do look better.
Me? I'm running an open top system. Will I loose fish? Already have. Had a clown jump on me, six months in. Haven't lost another in the six months since... Irresponsible? Perhaps, but this is a hobby... and if you're not going to be happy with your system, then why bother? I designed this system very carefully, low, fat, and wide. Beveled and polished rimless edges, a free floating, ceiling mounted lighting system... I like the look. It's got one clam in it now, and will have several more, in time. I really like the top down view of my reef, and I'm unwilling to give it up.
