The V8...
It has some serious grunt on the low-end. And with the all-wheel drive (I assume it's the quatro from the Audi A8), it's just so planted. There's no body flexing, either, which gives the VW a more vault-like feeling than the W220. The W140 is still a tank, I must admit.
The W12, from what I've heard from Audi owners, is to be avoided. The average MPG of the W12 is 18 combined - so this won't help me on 1,000+ mile road trips. The V8 gets the same 25 mpg on the highway that I get on the W140 (without even trying to be economical).
The VW's suspension settings are noticeable too. There's four modes, all of which I was able to discern. "Sport" gives the impression of less body roll, squat, and dive. In the W220, the sport mode was just "hard." The VW's comfort mode, although not as "old man" comfort as the W220, did soak up bumps.
The seats in the VW are also more comfortable... they are wider and have articulated backs. The massage mode is out of this world. And I don't recall which year the W220 or which models came with drive dynamic seats with massage. But in the VW, the massage, heating, and cooling was available in front AND rear.
When I compare a Phaeton to the W220 for the same price, the Benz doesn't hold a candle to the VW.
Depreciation is a nasty thing! I'm sure when the W221 hits the $20k range, I'll be wanting to dump a Phaeton for it.
It's just so tempting...