Thanks for the link, exactly what I'm looking for. What do you like Ubuntu over alternatives? Genuinely curious, I like the quick installation with the config program upon first bootup when running Rasbian.
You need a 64-bit kernel for the BOINC stuff, and I think you need at least some 64-bit userspace libraries as well. Raspbian is a 32-bit userspace and while it ships with a 64-bit kernel now, it's not used by default. It's harder to get all of that working than to just put a 64-bit OS/kernel on in the first place.
I wouldn't say I like it more or less, just that if you want the Pi to do nothing but run Rosetta tasks, Ubuntu is easier to get going.