Virgs, According to 90% of reviews, the 300 2.8L is sharper... That being said.. I dont have a 400 F/2.8 to compare myself... so i guess I dont know from first hand experience... I know the 300 2.8 is painfully sharp compared to the 500 F/4L.. the 500 almost always requires a little bit of sharpening in processing to get perfect, the 300 2.8.... I sometimes apply a gaussin blur, as its easier than a "Beware of sharp edges" sign..
