Shell Rotella T4 vs T6, what oil for CG engines?

[ProDigit]

I've been using the T4 15W40 oil on my Vader and other china bikes with success.
The T4 is a Jaso MA rated oil, and what that means is that it works for a wet clutch.
The clutch is a bit grippy, so I'm thinking of going to an MA2 rating, like on the T6.

The T6 comes in 5W40, 10W30, and 15W40 flavors.

The T5 is said not to be for wet clutches, however there was a few years when they did put the 'for motorcycles' logo on the jug.

I want to use a lighter oil for better MPG, but not sure if I can use any of the oils they make?

From the pictures online, it looks like the 15W40 and 5W40 is Jaso MA2 certified, but the 10W30 isn't.
Meaning, there's a chance the 10W30 will cause a slipping clutch.

I don't particularly need 5W40, as the weather here isn't very cold.

So I was wondering how the T6 15W40 compares to the T4 15W40?
Does it perform better, like, getting a less grippy clutch?