You've done the right thing getting the test drives, just make sure they are long enough to give you a full opinion.
However, from your comments on comfort and quiet, with reasonable maintenance then maybe the Lex is for you. If it's a purchase (rather than company car) then I think the general concensus would be 250 Auto if you can stretch to it, it does the same mpg as the diesel anyway! If not poss, then the experience of the three you've highlighted will be different so it'll be interesting to see what you decide.
Rich.