I can't say if the 6400 produces a better quality or sharper print than the 6300. I know that when the 6400 came out I considered upgrading as I had done from the 6200 to the 6300, but something in the initial reviews gave me the impression that it wasn't worth it. I use the 6300 and the 7900 differently. I do many event posters, and then also restore old theatrical posters and photographs from huge TIFF files. The new posters I print out on the 6300 because it's reliable and it does a great job. Really, the quality is supurb. I load it with a roll of paper and away it goes to the end of the roll. The restorations and fine art (if you will) I print on the 7900 because (1) I want the very best results, (2) they are going to looked at closely for quality, (3) I am only doing one or two at a time (4) I am changing paper in the 7900 fequently (canvas to matt to metallic for example) and it's a snap as compared to my experience changing paper with the 6300.