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If you care about aero it depends on your rims. If you care about Crr you need to think about the tyre material. If you're thinking about your wallet you might want to ignore those two factors.
Run what you brung. I think Vittoria Corsa and the Veloflex are still the fastest options but I haven't looked into TT tyres for a while. GP5000s are thinner and faster than GP4000s. I run 23mm tyres on the front for aero and 26mm on the rear for rolling resistance (using Corsas with latex tubes).
Realised my GP 4 seasons are completely shot, any recommendations for something to replace them with? The bike is still my general road bike, so was just gonna get 30c gp5000 from Merlin cycles (or is that a terrible choice for a TT?).