It always depends on the demands.
What kind of demands should one have? Tight? Pole can do that too. Letting you look outside? Did he invent glass? Handle to open and close, he can do that. Profile not flimsy? Well, he buys them anyway from the big brands, except Drutex, he is big enough to manufacture them himself. Drutex is also pretty cheap. U-value? As if that were an art. You just take three panes instead of two and the thick profile, the Germans want it that way, U-value is cool.