[jparnes1]

This from an M3 board. Hope it helps:
BMW uses Merino leather in the M5, as they do in some 7-series cars, while dakota leather is used for the regular 5-series/3-series. Merino is a thicker and higher quality cowhide that typically doesn't have any additional surface treatment or graining compared to other types, meaning they have to be selectively picked from good batches. it is one of the softest types available yet maintains durability. Nappa is thinner, not as soft, more prone to scratches, but is often preferred because it feels smoother. Merino does retain more of the leather smell that people like though. I'm guessing they used Nappa for the M3 because it is cheaper, and perhaps because it's lighter?

For what it's worth, over the same period of time, the Merino leather in my M5 has held up much better than the Nappa leather in my RS4. I haven't treated or cleaned the leather on either car yet. The M5's Merino seems more resistant to scuffing, scratching, and especially folding and creasing. Two years and 13k miles later, it still has that strong smell of new car leather when I get in. Not so much the RS4 after 12k miles. Its Nappa smells like butt sweat, looks kinda weathered, and has so more wrinkles and creases than my 45 year old thrice divorced office assistant with 7 kids.

I'm very curious to see what Novillo is like. Hopefully it'll be more like Merino.