Yes, build quality. Ignoring the outer case, overall design appeal, etc. -- the inner guts are either built well, or they're not.

When you grind something between two pieces of metal, if the pieces of metal can wiggle or bend or move, you end up with inconsistent coffee grinds. Big boulders, tiny fines, and everything in between.

If the metal parts are rigid and uniformly spaced from the factory, then you enter the territory of nicely ground coffee. There are fewer outliers, and most of the grinds are of similar size.

This all translates into coffee that's easier to brew because the water flows through it easier, and coffee that tastes better. The big boulders will be under extracted (sour), and the fine particles will be over extracted (bitter). The stuff in between will taste good, but the sour and bitter stuff might "ruin" it.

The Baratza Encore has been a go-to recommendation for years, and if you're on a bit of a budget that's what I would get. You absolutely get what you pay for with coffee grinders, so if you're flush I would skip the Encore and get something 3x the price. "Buy once, cry once" as they say.