Funny. In the U.S., it's the opposite; G48 is only available as an OE coolant (BMW, Saab, Volvo), while G-05 is available both as OE and aftermarket.
They're very similar, but G-05 is nitrited, while G48 is not.
I researched the 48 and 05 for my bmw. The chemistry is slightly different, but the wear/corrosion and inhibition were very similar. I used g05 without isues for a fair amount of time, for a few years and tens of tgousands of miles. Maybe not long enough to manifest itself perhaps... And I've gone back to g48 since.
Kind of a non answer, but I found no significant difference, and practically, I think they are interchangable to some extent.