Advantages to each. The Pixma 9500 will give you a touch better quality print due to its 10 continuous ink colors with the LUCIA ink system, and 7680 nozzles. It is limited that its print size is maxed at 13" x 19".
The Epson R2800 has 9 ink cartridges but they are the standard epson chromo system, with fewer nozzles and less resolution allowance. It will however print up to 24" max width.
Both are comparable in price in the $800+ range.
My personal opinion is the canon will produce a better quality print.
The question is, do you need this level of printer? The Epson R1900 doesn't have the quality as the R2800, but will cost around $300 less. As well as the Canon Pro9000.