Here are the comparative noise figures for the Mullard AT6360-02 (valves) and AT6380/02 (transistors) UHF tuners:
At the top end of Band V there was quite a difference - <14 dB for the valve tuner and <11.5 dB, typically 10 dB for the transistor tuner.
I’d expect though that the transistor tuner had a lower signal handling capability than its valve counterpart, perhaps not too much of an issue when getting enough signal was the bigger problem in many locations.
D.C. Read (of the BBC, I think) commented about the narrow signal range window in respect of the later ELC1043 UHF tuner:
Cheers,