Sorry for the late to reply to this message, but I've only just discovered this website - very interesting!
I had Audi's as company cars in the UK for 5 years before I moved out to Japan - 2 A4s and an A6. Now I'm working out in Japan, and am using an Altezza AS200, which is a Lexus IS200 in the UK.
In comparison to the 1.8T engine, the Toyota inline 6 is very smooth but, esp. when mated to the auto as mine is, it's not exactly quick... More of a cruiser than a out-an-out performance saloon. Hopefully the manual transmission is quicker.
As people have said, equipment levels are probably much higher on the Lexus. Style is a matter of personal taste; some find the Toyota/Lexus a bit 'flash', and certainly the quality of the interiors trim is not up to Audi A4/6 levels - can't comment on the '3 though as I have never owned one. I also can't comment on the Lexus dealer experience for you, but it's bound to be better than here!
I got used to my car being collected from the office, serviced, cleaned and returned to me by Audi dealers in the UK - here the car is not even cleaned, and as for collect/deliver or a loan car...
Hope you enjoy whatever you choose!