It really depends on the rider.
The two bikes I ride on brevets have 34f/36r and 28f/32r low gears. I rode 34f/32r on PBP and was missing the 34/36 gear a couple of times. But I'm using a 10 speed system on those bikes so I have plenty of gears, not the case with a 5/6 speed freewheel.
My rationale for having low gears like that is that suffering over a steep hill causes problems that don't happen with lower gears. Lower gears mean you don't have to eat quite as much.