Less VII in the 5w20 is a positive. I would be inclined to go high end synthetic on these ligher weight grades. Redline maybe the most robust. Somewhat depends on the engine and driving style.
I just switched from 0w20 Amsoil ASM to PP 5w30 in my '08 Mustang GT 4.6L 3V engine. The engine is noticeably smoother throughout the RPM range on the 5w30. My wife even commented on it and asked what I had done to the car. No noticeable change in performance or mileage.
My reason for going to the 5w30 is the higher HTHS numbers (3.0 vs 2.6). I also like the fact that this oil meets the GM 4718M and Acura HTO-06 specs and that it meets ACEA A5. I'm betting my wear numbers on the next UOA will be excellent.
We have a '06 Mustang GT w/40,000 mi on it and a '06 F-150 with 13,000 mi on it. Both are spec'd for 5W-20 that I run 5W-30 Maxlife syn-blend in and both love it. Engines seem quieter and gas mileage hasn't changed any.