I have dozens of hubs either in boxes or in wheelsets. Bottom line is that the mid-range Shimano hubs are unbeatable in terms of design, quality of materials and execution.

They feature loose balls, but they are 'sealed' - very well indeed. Usually better than the overpriced overhyped cartridge bearing product from the small-fry manufacturers.

I am looking at a stack of boxes of hubs that includes Novatec, Hope, King, Campagnolo (many models), Mavic etc. If I were to build a set of wheels for myself right now, and did not worry too much about a few grams of weight, I would reach everytime for Shimano LX or 105.

BTW: the shop you went to are idiots. Or more likely liars.

And if you are considering cartridge-bearing hubs, apart from the sub-optimal design relative to Shimano, consider the misery you'll have to go to find and replace some obscure cartridge bearings down the road. Or a rare and expensive freehub.

Shimano hubs and replacement parts are everywhere. I don't even pay for these, as they can be scavenged from wrecked wheels at the back of your local shop.

Finally, with respect to the argument that certain bearings have lower friction or 'resistance' than others... Hub energy losses are negligible. Don't get fooled into paying for something idiotic like ceramic bearings.