depending on how much you care, or bothers you the glossy case of the DAS, I would go with either the DAS, or the filco.
If I'm not wrong, as far as I've read, all the keycaps from this three keyboards will get shinny at about the same point, but have for sure, that at least the filco and DAS, won't wear off, I haven't read much about leopolds, but the otaku has blank keycaps so... Also I would go for the DAS with blank keycaps, and the reason the DAS requires two USB ports, is cause one is for the keyboard, and the other one is for the USB HUB it has on it, so if you plug just one, the USB hub won't work, no need to plug it if you don't plan to use it.
I been thinking for long, a solution for those who hate the glossy case of the DAS, I know a store on Chile, where I've made my universitary studies, where you go with whatever you want to customize, and they make custom sized stickers made some special material, much more like for laptops tops and inside, it dosent wear off easily, and if you decide to take it off it doesn't leave any gross residues on the laptop/keyboard. You could make a custom colored one and have your das pimped.