I've read the various posts on this thread & respect people's feelings.
My opinion is I don't find size discrepancy a huge (pun intended) problem.
Sure there's some sets that are unusable but mostly if you keep them in discreet units it doesn't matter.
Revell, Wodenfeld, HaT, Imex, Esci, Zvesda & more: here's my 7YW armies in action:
I see your point. At this distance they all look the same size to me!
Nice scenery here. Did you make it, buy it, or both? I especially like that star fort.
As for my own armies, I buy whatever is made that I need, regardless of maker, within reason. I won't buy 28mm plastics because A they're designed to fit with similar metal figures;B they're way outsize compared to 1/72, and C they're way too expen$ive to be building my armies around.
In my scale, I have Airfix French Grenadiers fighting alongside Italeri infantry and Zvezda artillery. I'd prefer them a little closer in size to the others, but not many Grenadiers are made in full dress; most are in campaign dress, and I have a huge stock of Airfix figures of all types, too many to try replacing at this date!