I have rented the 70-200 F4 and own the 70-300 IS USM. I also own the 70-200 2.8 II. I have never tried the 70-300L. I think that the 70-300 IS USM is a great deal if you want the extra reach. It has nice color and good sharpness for $500. If you want the great color, sharpness, and detail, then I think the 70-200 F4 is the way to go for around $700. All the best.