With my tank I went with the thinnest starboard possible, 1/4". I did not go bare bottom, but with a VERY thin sand layer and wanted something to protect the bottom pane. Some people glue the edges of their starboard, I did not. So far I have had no warp-age although I have only had it in there for about 5 months.
As far as Black and White, I went with Black and have no regrets. If I went bare bottom I would definitely go Black. I think the advantage to White is if you have a thin sand bed like mine and there are some bare spots, they blend in better. But my tank has a black back with black silicone, black overflow, etc. I just wanted to keep everything black and I like the look.