Rarely will you go wrong with an L... if it's even possible. A bonus the F4 iterations are going to have is slightly sharper edges, just cause they're a smaller lens to work with. (or so I hear..) All of them are going to be sharp, all of them will have fantastic contrast and really pull the colors through. Don't think you're getting jipped cause it's 'just' an F4, having it be constant from 70-200 is nice as most consumer grades are hitting 5.6 on the long end which is too slow.
I'd look into investing in the battery grip for your body as well, as mentioned it's a long big lens and having that extra support for your pinky etc to keep the lens forward is nice.