So, first impressions:
How does it compare to the Mini "out of the box"/bone-stock?
That's a little hard to sum up, because my MINI didn't stay bone stock for long. But I can say this:
The ride is softer, smoother. Definitely nice for cruising. Seating position, while higher off the road deck, doesn't feel like an SUV, thank goodness. I had good visibility all around, with only a minor spot of blockage at the C pillars. Nothing that a thorough & peoper mirror check plus head swivel cannot overcome. (I do that anyway- paranoid about people in my blind spots)
Compared to the Cooper S (I never really drove a base Cooper) it lacks a little of the pep, especially in 5th gear (MINI has 6). But it is certainly not weak. The clutch/throttle is a little tricky/twitchy, but I am sure will adjust. Did not expect the clutch to engage so high up. Might ask the dealer to adjust it lower (if possible) before I take delivery.
Seating is a little less supportive, due to the miniscule side bolsters, but the overall seating position is fairly comfy. I think it would take longer on a long road trip for my arse to fall asleep.
Didn't really crank the stereo, but I did fiddle with the dials & such. It definitely has more wow/bling factor than the MINI unit.
Overall front passenger room is probably pretty close between the two, believe it or not. Due to its raised console around the shifter, the xB actually seems a bit more snug on the driver's side. But that may just be psychological. MINIs to have a LOT of front passenger room, though. My 6'11" friend Norm drives one, too.
Rear seat room, no contest. I have had 4 adults in my MINI, but only for short trips. I sat in the back seat of the xB, without scooting the driver's seat forward, and I had all kinds of room. Once again, I can be the guy that drives when I go out with friends!!!
Ditto for cargo. The MINI would surprise people once you folded the seats down, but it's simple physics- the xB is larger & has more uesable cargo space, hands down. I also like the little storage cubbies under the rear deck. I like to carry jumper cables, tire plugs, 12v compressor, etc. and that gives me a place to stow it all.
The xB doors feel a little thin/lightweight/less substantial compared to the MINI, but then I am comparing the longer doors of the 2-door car to the shorter doors of a 4-door.
I'm getting acid reflux from stressing about trading in my MINI, but I'm sure I'll get over it. Someday.