engine oil viscosity question

[ybk at dongames.net]

I have been using 10W40 
http://www.amsoil.com/storefront/amo.aspx since I bought 
my car in 03 (280k + miles now). When I got the 12 quart 
case last year I noticed that the label has changed (UPC 
code has not) and there is no "Volkswagen 502.00, 505.00, 
505.01" listed on the bottle. I still used the case for 
all my cars but this year I decided to do some more 
research and found that "Volkswagen 502.00, 505.00, 
505.01" is listed only on 5W40 
http://www.amsoil.com/storefront/afl.aspx oil.

Please suggest which one is better for year round usage 
including one or two high speed events.