I am also topless.
I've used both glass and eggcrate. If I had to choose between glass or eggcrate, I would choose eggcrate.
Eggcrate does diffuse the light, but it won't promote salt creep and allows for better gas exchange. If you have MH, you have to be careful not to melt the eggcrate.
When I used glass, I always had terrible salt creep. The glass needed cleaned a lot and it eventually just gets imposible to clean and blocks a lot of light. It doesn't allow for as much gas exchange, but if you have a sump this isn't a big issue, however if you have an issue with keeping your tank warm, then glass helps hold heat (which is also something to keep in mind if you have over-heating issues).
Overall, I would just go topless unless you keep fish that are notorious jumpers (in which case, I would go with eggcrate).