Help decide: 100-400mm L or 300mm L 4.0

OK the money is ready and the 200 2.0 is too remote to consider =:o so I'm ready to go for a long lens.

It comes down to this: 100-400 or 300L 4.0. I have read all the reviews, so I know pretty much what to expect. What I would really like is some actual user input from people who can compare their impression of the two to each other - or to the 70-200L 4.0 IS which I have.

My biggest worry about the 100-400 is slow auto-focus and somewhat washed out colours compared to the 300L. I expect no (unpleasant) surprises with the 300L.

For use on crop body (Xti). Primary motives: portraits, street shoots and beach & sea

Other relevant lenses in stock: 70-200L 4.0 IS and 135L

(I know the 300 2.8 is wonderful, but it's too big for me. The 200 2.0 looks OK, so I will likely just use my new lens a year or two until the 200 comes down a little and then go for it with a 1.4x option when I need the stretch. Resale ease/value of the two lenses above is therefore also of interest if there is any difference).