>>Making nucs from your worst hives will give you poor splits.
When I take my colonies south for the winter the poorest ones are the ones that don't survive.
Make your nucs from strong hives.<<
You're comparing 4 or 5 frame July nucs for overwintering, with nucs made for building strong colonies to overwinter. It's different.
The whole point is to use the weak colonies for making your nucs. All you need is a frame of brood and bees...maybe a frame and a half. You use the resource that's in your weak colonies to your benefit. The nuc is requeened with a laying queen or a cell. They're only supposed to build up enough to fill their little chamber. They winter just fine.
And, now that you don't have to split your strong colonies, in the spring, to replace your winter kill...remember, you made nucs last July from your non-productive colonies...you can let them make honey.
Best of both worlds.