I like both colours (having owned 2 cars previously in similar colours)
specifically for the mk6 gti I've seen it in silver in the metal and it looked really good. quite a futuristic feeling - will be even more so with xenons
goes well with the alloys too.
the blue looks very nice, tho the pics below are perhaps overly shiny to make a fair judgement on it. also i think it's less of a GTI colour and more an R32 colour!
if you pushed me , I'd go silver.