have to disagree with you there... you cannot base it on just
one sit...
I owned a lexus GS300 and a BMW E39 528i and a Merc E280, so all
pretty comparable.
The lexus is ok on first impression, but the more you drive it, the
more its handling characteristics irritate you. There is not enough
feel through the steering and it does not talk to you as much as
the BMW.
I still have the BMW and I love driving it everyday even though now
it is a superceeded model. The merc is somewhere inbetween the
lexus and the bm...
The lexus also was too floaty in my opinion. The engine is good,
but when you compare it to a comparable engine like in the later
530, you will realise that the BMW has a better engine. Testament
to this is that the bm engines have been winning best engine for
something like 4 years in a row...
The other thing that really irritated me about the lexus is that
everywhere you looked in the car, it said toyota corporation
japan... 
The lexus is too gadety. The seats in the BMW are more comfortable
overall, especially over long distances. The merc seats are worse
than a lexus. NO support at all.
The lexus gearbox is also not as smooth as the bm I find. Forget
the merc... way too slow.