I'm fairly certain that either option would be good for trucks. I'm mostly referring to motorcycles that share a sump for both engine and transmission lubrication.... Some people say the 5w-40 shears too quickly in that regard. Theoretically, it should.... but I'd rather stick to a 15w-40 if at all possible.
I believe the Rotella T6 *15w*-40 actually is the first synthetic 15w-40 for gasoline engines. I think the big 3 "primo" brands (royal purple, amsoil, & maybe redline even? so maybe just 2 brands?) have synthetic diesel rated oils in that weight.... but not gasoline rated oils.