The Canon printer is a better value, however I would buy the ipf8100 not the 6100 because it holds the 700ml inks and gives you more options to lower the cost per print. Canon support is better than Epson at this point. If you don't have experience with Canon professional support (and are used to their baby printer support) that would be why buying an Epson for support reasons was a "no-brainer" for you.
Epson clogging is still a multi-page thread on this forum for the x900 which I was highly surprised to hear and it's looking like ink waste will sway heavily to the Canon as it always has. I'm not sure which costs you were tracking but I can assure you an Epson will cost you more in every respect.
Note: Ink prices are far less than the cost of good media (paper) so many people get overly concerned about cost per print, not realizing that the big issue is really ink waste especially when clearing Epson clogs where you could easly pump hundreds of dollars of ink through the nozzels in one long cleaning session.
How is the Canon the better value? It seems like the ink cost for the 6100 is about 50% more compared to the 7900. You say you would buy the 8100, isn't that the 44" version? Canon support is better today? OK, I must admit I wouldn't know who is better, it's been a long time since I used Epson support and I have needed Canon support (for cameras and smaller printers) and found it lacking. I'm assuming you know Canon support is superior because your printers have needed lots of support? That's generally how we know how good support is. I know Mercedes Benz has a great service department because of my 3 new Benz purchased since 2006 2 of them had their trannys go, 1 at 196 miles (Mercedes bought the car back) and one at 25,000 miles. The service was great, but the damn cars suck! Apple, I bought 3 IMACs, all 3 died, the service was TERRIBLE. Needless to say, I don't buy the Epsons because of their superior support but rather for their superior quality.
Ink clogging; there's no doubt there's been a lot of well documented issues with ink clogging, nobody can dispute that. However; I still have a working Epson 1280 that was purchased about 8 years ago and it has never had a clogging problem. Sure it needs an occasional head cleaning, but it always works. I think the environment might be an issue, who knows, some people have the problem and others don't.
Aren't the Canon print heads replaceable? Isn't that a part of TCO? So, the ink costs of the 6100 is substantially more and you eventually have to replace (in the Canon) $1,000.00 worth of print heads?
We tracked the costs of the printers based upon a couple hundred prints using the same paper. We just got curious and decided to run a bunch of identical prints from both our Canon and Epson printers and we found the Epsons were less expensive to operate. We print a lot and I mean a lot of prints for clients (we design / build houses / additions / interiors and give them prints of their project designs, the before and after photos) We started out using Epsons, but they were slow as hell and so I started buying Canons because they were about 5 times faster. Well, what happened was people started calling telling me that their prints were fading and they wanted to keep them for posterity (archive) so we would give them Epson prints. Naturally Epson started to catch Canon in the speed department and Canon caught Epson in the quality department IMHO and so now we can go back to using Epson exclusively.
The Epson printer is more expensive, but it wont take us long to recoup the costs in ink because we do print a lot and we probably wont have to replace the print head which on the Canon is $1,000.00 and I have read about many people paying for new print heads, I think it's just the nature of the heat in the Canon and HP heads.
There's also the matter of Karma, some people just have better luck with one brand over the other. I used Nikon cameras for 30 years and when I started using digital I switched to Canon, nothing but problems, switched back to Nikon and now I'm in "Digital Heaven" I've always had great luck with Epson, I'd read about color shift and head clogging yet I wouldn't have the same issues. HP lasers, never an issue, as a matter of fact my friend still uses my old HP 6L from 1998, many of those had the paper handling issues, multiple sheets would come out together and you needed to install a paper separator, if you had the problem, I didn't. Epson scanners, great!
You probably can't go wrong with either printer, but I'm not sure that the TCO of the Canon is less than that of the Epson.