As far as control panel building (at the factory where I work) is concerned, I've always been a fan of black or stainless steel mesh with angular holes, round holes kinda annoy me (don't know why), I like hexagon stamped mesh best, then square stamped mesh next best, and the woven polished mesh comes in at third, but it's easier and cheaper to get and for some reason you hardly ever see it on PC builds? I would use this for a PC (if I was planning to build another one), framed in black powder-coat steel, it would look nice!
but for retro PC builds I love those chromed fan gratings you can buy off electric wholesalers, they look so good in rows on server cases etc...