Need a new Printer - should I switch from Epson to Canon?

I currently have two Epson Stylus Pro 9900s and an Epson Stylus Pro 7800. One of the 9900s is 13 years old and needs at least one new printhead. So I need to buy another large format (44"). I'm debating about switching over to the Canon imagePROGRAF PRO-4100. I see that you can change out the printheads yourself, it has a built-in hard drive, and I can add a second media roll holder. I have checked the ink cost and it is pricier than Epson (about $315 vs. $245 each), but I believe it can use all the same paper media. The hard drive sounds great, but I wonder really how much I'd use it anyway. So, if I stay with Epson, it looks as if there are maybe two contenders (not sure what the difference is). There is the SureColor P9000 Commercial and the P9570. I work at a college and print many posters and indoor banners; but also fine art and photographic prints. Can anyone give me advice or any experiences they've had with these printers to help me decide which to go with?

I also hear a lot of talk about using a RIP or Fiery, but I've never used one and have no idea if it'd be any benefit to me. I am a graphic designer that has built up this design/print shop on my own for the past 20 years. It seems to be working fine, but I've had to learn it all on my own as no one else on the campus has any experience. So if you have any suggestions, that'd be welcomed too.