The Amsoil 10w-40 will tend to shear a bit during the first 10,000 miles and then start to thicken back up after that point. The Amsoil 10w-30 may actually show a bit more relative thickening after 20k-25k miles, since it's more shear stable. The 10w-40 does use an SL/CI-4 additive chemistry, so I think it will keep the engine a tad cleaner ....
Wear protection will be very similar with both oils, but you may see a bit less bearing wear with the 10w-40. However, the friction modified 10w-30 will provide a fuel savings of perhaps 2% over the entire drain interval and will reduce your peak oil temps by 5F-10F.
I started out running the 10w-40 in my Audi TT roadster, and now have about 8000 miles on the 10w-30. Oil consumption has been the same with both oils, but subjective engine performance and turbo response is better with the 10w-30. I haven't tested the 10w-30 yet, but wear was very low with the 10w-40 I tested back in the spring. ....