I'd pick the TSX. I love the exterior and interior of it. As for the IS300 I like the exterior more tha the TSX's but I do not like the Iinterior at all. Since you spend 99% of the time inside the car, the interior rates high on the importance factor for me

Here is the comparison of the two cars on Acura's site:

http://www.acura.com/models/model_co...asp?module=tsx