Whereas the BMW has a world renowned machine that is really capable and fairly dependable, I voted Bonneville. The Bonneville has absolutely made a name for itself, and I like it a lot for this reason. Plus, you save money. Beamers are a bit more costly to maintain from a parts cost point of view. My uncle has a similar BMW in Germany. It'* a bit older, though. He drove my dad in it on the Autobahn, and my dad says it felt great.
My godfather'* daughter (godsister?) has a BMW 3-series, and it'* really nice. It'* comfy (only in the front, whereas the back is like a wooden bench), and it feels really solid. One day, though, it just stopped in a parking lot and wouldn't start back up. It needed a reported $600 repair to get going again.
So, same with the 01 Alero my sister drives...
I think the 5-series BMW has a nicer interior than 2000+ Bonnevilles.
But the Bonneville is cheaper, IMHO better looking, and overall bigger. Let'* see what others write.