I invested quite a bit of effort into designing URLs for the PartsBox ID Anything™ system so that they fit well into optimized QR codes. Uppercasing was one of the tricks, and it makes quite a difference indeed. This is important when you want small and yet easily readable/scannable QR codes.

Later it turned out that when printing labels, you hand your data off to the printer to produce the QR code anyway, and printers do not try very hard to find an optimal encoding.