Some good points. Here is my take.
1.) If you examine the specs, it is clear to me that Amsoil is better.
2.) But, Amsoil is not API certified and if you should ever have a oil failure, Toyota may not cover it as you are using a unapproved oil.
3.) If you go over the recommended change interval set by Toyota, once agian Toyota may not cover your repairs. Amsoil does have it's own warranty, I have heard of one case in which a Lexus formed sludge going on the extended oil change and Amsoil did not cover it.
4.) When I changed last week, I noticed Mobil 1 specs have gone down since my last change. In other words they are cheaping it.
----------------------------
Conclusion, at least for me: If you are under warranty go with Mobil 1. Then change after the warranty if you want. Also, I would not go with extended oil change. I thought 25,000 was high, but in my opinion going 35,000 miles is simply asking for trouble, not matter what oil you use.