WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I honestly don't know, I think for a low-rp triode such as GM-70 it does not make a lot of difference. You have to decide how much money you want to spend on them.