Well, one thing you've already mentioned is the design. I personally like the '04 way better than the '03. '04 has the projector bi-xenon headlights, bigger body, more sturdy, more safety features like side curtain airbags (resulting in better crash test rating), and LED tailights to name a few.'03, on the other hand, has better quality leather seats and less rattles. Rattles were issues on the '04+ TL's. However, '03's are pretty much guaranteed to have tranny issues. I may be wrong but a great number of these 2nd gen TL's suffered from the transmission problem unless you got the manual. Some early '04's were also affected I believe. Make sure to check on that before you purchase.On top of that, to me, the '03 looks pretty outdated.I'd definitely go with the '04. No question.