Comfort? At 4.5 million? Lots to choose from... don't limit the choice to just the two... and are we talking brand new? Volvo S80s are pretty nice in that price range... but a good investment would be a new Bimmer.

New Jags are very comfortable, very posh and have a great old world charm. Real wood and leather add to the appeal. Some people find the interior a little small, but it's cozy and warm. Don't know if a new XJ6 fits into his price range, though.