Magnum

The Lexus got more creature comforts but the Altezza was not too far behind. The differences were mainly there because of market preferences/practicality. And yes...where performance variants were concerned the Altezza was handed out with far more offerings than the Lexus. 

At the end of the day..none of these badges matter. In SL it is all about the letters on the number plate....if it is not a new lettered number plate...doesn't matter whether you are driving a million dollar Jag from the 90s...you are driving an old car (usually the reason is because you are having trouble in your career that you cannot afford a three digit Premio/Allion or a Land Cruzar Parado.

Not sure about creature comforts but the Altezza was a better car in terms of performance.
The 3SGE on the Altezza was lighter compared to the 2JZ on the IS300, as the 3SGE was 4 cylinder the engine sat further behind giving the car a better weight distribution, Altezza had a six seed manual option and the 3SGE has heaps of aftermarket mods in Japan. Altezza also received some aero options.

Like I said..the Altezza was handed out with far more performance offerings. As for the 3S-GE....to be honest...I like the less strained smoothness of the 2JZ. The 3S-GE at the end of the day just feels strained and not very smooth. Not that it is a bad engine..just that the 2JZ is a much smoother engine to drive. the 4 vs 6 cylinder running makes a difference.