Ah, But a head can be so versatile by mixing and matching different cabs and speaker combinations.
I've got a Blue stripe med. Head with simul / EQ / Reverb and 6 cabinet options to run it with. Each with different speakers or speaker combinations.
I've played different stripes but this is the only one I've owned. I make no claims to it being better or worse than other stripes. They all are great in their own way.
For example, I own the blue because I think it's high gain channel is equal to the red stripe and prefer it's Marshally R2 channel over all the others version's R2. Actually, my blue sounds more Marshally on it's R2 channel than my Marshall does. On the other hand I think the clean Fender R1 channel on the green or purple is better than the blue. I've never played the black / no stripe but imagine it's got some big pluses of it's own.
Honestly, I don't think any of the stripes can lay claim to having the best of all three channels. Thus, No grail.
But, before Mark IV owners start saying you should have bought a Mark IV I would like to add that I think the Mark III red or blue stripe comes closer to the grail high gain tone of the Mark IIC+ than the Mark IV does.
It's just my opinion. I'm happy.