You're right on with the reasons you listed. Here are mine:
1) I have had the platinum for 7 years now. The foam padding is starting to break down and compress more than I would like. As with you, I don't feel much when I get hit, so I'm not doubting the protection. I would rather fix it before I do start to feel it.
2) I like the idea of a slimmer looking protector. I'm not the smallest guy, 6-3 225, so any reduction in the bulk will help lol.
3) The extra protection of the TW padding is definately a bonus. Seems to be the best protection and most advanced material on the market. If I'm going to be getting hit, I'd much rather be wearing the best possible gear I can.
From all the research I've done, the TW retro seems to be the best solution for me. I don't want a new CP, I love my platinum, just some modifications and improvements. The slimmer profile and new padding would have sold me, so the beefed up protection was just a bonus.