I think that it comes down to individual preference- Seeing the minor difference in just a CPU loop would tell us that it makes little difference what diameter we use. So if I was trying to watercool in a Shuttle case, I would use 7/16" ID 5/8" OD with some Coolsleeves to make those super-tight bends. At the same time, if I was watercooling in a Mozart case, I might go for 1/2" because there is no need for a smaller diameter tube and I can afford to lose space in such a big case.

I still would like to see a test done with at least another block. I vote Fuzion + a GPU block. Why? Because I think the differences might become more apparent as we introduce more restriction into the blocks.