Hi Wah
I have used 45 and 801A output valves (the latter being higher-rated 10 types) and found the 801A best for Lowther/Lowther-type speakers. I believe it is due in no small part to the higher impedance driving the intrinsically highly damped drive units.
I also find the "thoriated-tungsten sound" more subtle than the more prosaic 45.
However, I do believe the two types of valve to be the very best for playing music through efficient speakers and final results will depend on the driving valve(s) used, output transformer and power supply.
Brian.