I looks like the soft lines are split into two sections, which isn't uncommon. But I don't see a reason to replace the hard line unless it is corroded.
As far as OEM vs SS lines go on the X5, I am not sure. I do agree that most of the feel probably comes from new lines compared to old lines instead of rubber to stainless steel ones. If the OE ones are in fact braided steel that would work. The OE ones on my E30 are braided nylon, and have since been replaced with aftermarket SS ones.
460 seems outrageous though. ECS has the genuine BMW ones for 180, and ECS is typically on the high side.
As far as corrosion goes, after a few years my SS lines do not seem to have worn at all, even with many trips up the pass and to the mountains. I'll replace them if/when I start seeing fraying though. I have probably 20k miles on them along with track days. Although we don't have the same corrosion problems in the PNW as we do in other parts of the country.