I just read through a web page where the author prefered the Mobil 1 over the Pure One because it appeared to him like it would flow very well and had not found any flow data for it. In his opinion both filtered well. He had no comment on the Amsoil filter other than it looked like good construction, he hadn't really done a full review on it yet.
I'm thinking about running a Mobil 1 EP filter with Royal Purple oil on a 6-12 mo OCI since I will likely put significantly less than 5k on my 4Runner in a years time.
I also have an Amsoil connection so I could go 100% Amsoil products, but I like being able to pick RP up at the local stores.
1989 Toyota 4Runner / 5w-30 Pennzoil Platinum
2004 Toyota Sequoia / 5w-30 Mobile 1 EP
2008 Honda Civic / Unknown