A big factor in determining block performance is knowing how restrictive it is. Knowing how restrictive it is, as well as pump performance and how restrictive the other components in you loop are, you can know what flowrate to expect. Generally speaking, you don’t want flowrate to go too low–every component performs better with higher flowrates (but to varying degrees). Ultimately though, higher restriction is fine because it’s what you do with the flowrate that’s most important–flowrate is a means to get lower temperatures but flowrate without context is pretty meaningless.
Of note, “Restrictiveness” is a unitless metric measuring restriction and is effectively, not literally, an inverse of measured flowrate–lower means less restrictive. It’s a sum of pressure drop readings at the eight lowest pump settings we test.
We’re still early into the 2011 CPU Block Comparison, but it’s already clear that the Supreme HF Full-Nickel’s restrictiveness and flowrate are non-issues; restriction is low.