I'm renaming this post due to straying from the OP's questions. I expect the image quality and workflow for ABW work from those 2 printers to be probably identical. So other feature options would determine the choice.
These discussions about either equipment or workflows, using descriptions like "better", "very good", etc., get problematic. On another list I found myself talking to someone who considered "best"' that which gave him the most options and flexibility later, so he shoots digital, obviously then rgb, and converts later using the various tools available to do so. So he considers the ability to leave critical decisions for later, and lots of conversion flexibility at the digital stage, more important than the potential gains with skilled exposing and processing B&W film to yield more flexibility at the scene, and final print quality someone like me finds "better". I also do "better" work committing to some shoot discipline, committing to sheet B&W film, fixed lenses, and telling myself (to this day) cropping will not be allowed. I can't leave state of mind out of the mix. Additionally, the print quality I love from large format scanned B&W film printed with monochromatic inks is not really recognized by the RGB capture guy, or at least it pales in comparison to his issues.
This relates to another recent thread about the "best" way to covert from color to B&W on this forum.
Anyway, Peter, I'm not picking on you but your post sparked more of some of my favorite rants...
To a greater degree than ever, many committed photographers have less knowledge than ever about the physical makeup of their prints, I am pointing at inkjet. Many workers on this list are well versed in the particulars of the darkroom papers they use, and the chemicals, many mixing their own, and the alternative process workers would be the most extreme of example. This level of involvement was considered accepted and normal, for many. With inkjet, it's very abnormal, and one must go out of ones way to learn anything about it.
On this list amongst a community of large format workers, one must assume the qualifying terms like "better" apply to long held craft standards of the medium- optical clarity, continuous tone, materials longevity, amongst many other concerns, are what we are talking about. So given that assumption I have to take issue with some of the posts...
Never before did we expect the convenience of both fine black and white, and fine color, from the same systems and materials. Even though we may be able to hit mono print hues on type C paper not otherwise available, no demanding monochromatic worker would have found that route acceptable. Now, we do. We are making B&W prints with color materials, machines, workflows, with little knowledge of any of the particulars.
With regard to longevity, clearly color inks fade at different rates. A monochromatic tint composed of a build of highly saturated CMY, and some K, inks, clearly will not maintain that particular hue over the life of the print, even if it is long in terms of acceptable density fade. In this regard, the less color inks present the better. With UC 3K Epsons, color inks are in highest use with the RGB driver. In ABW mode, much more of the core of the image is made up of K, light K, and light light K. Unfortunately not as much as possible, there is still a significant amount of color ink present in the ABW prints. Clearly the goal would be to use K, LK, and LLK as the vast majority of the image from black to white, with the addition of only enough color inks to hit the users desired print hue. This was the genius of ImagePrint, when it first came out it was probably the only out-of-the box solution like this. Now we have QTR, setup up (with provided ink curves) to do the same. Highest possible utilization of the K inks for the entire scale, with the option to blend in cures that use minimal amounts of color inks to suit. I would advise anyone happily using a UC 3K printer for B&W to learn QTR for this and other reasons. For supported printers, it's very easy, also totally user tweakable for those with the aptitude. At a workshop earlier this year, we had people making QTR prints from a 3800 after a brief description of the needed settings, prints were immediately more impressive than the ABW prints participants brought with them. Plus, they thoroughly enjoyed fine tuning the hue of their prints, separately in the highlights, middles, and shadows. ABW can't do that, only globally. Obviously, on this topic, the dedicated monochromatic inks sets are most appropriate, with no hues made by combining dots of individual saturated color inks.
This same progression of quality applies to photographic image clarity. When a color value has to use up many available dot positions by dithering CMY and K, it has to give some up that could have been used to describe detail. My testing shows available detail from the file is most transfered to paper with the multi-density monochromatic inks, followed by a well set up QTR UC 3K system since the highest possible density of LLK, then LK, then K, then the least necessary color inks, will be used, keeping dithering tones to a minimum given the system, followed by ABW, and the RGB driver last. If one understands how these different systems work, it's no surprise.
Similarly, with regard to continuous tone, more and more micro levels of gray in the file are tossed out by the system as we go from K7 monochrome inksets, through QTR, ABW, then the RGB driver.
If one visualizes these systems as complex half tone, perhaps it gets easier.
I want to be very careful to clearly state that these particulars may or may not be visible given source material, subject matter, capture, film, scan, paper, eyesight, etc.. Also, it's clear that these issues matter more to some then others, and I'm not saying they SHOULD. They are a concern of mine, so I look into them, and levels of performance with regard to these issues and others are part of the craft of our unique medium. I have to also state unequivocally that it is very possible to make a subjectively "better" print with say, the RGB driver and color ink, than a fine tuned K7 setup, because we all know it's about more than processes... however I think we have to be careful when we talk about systems being "good", "better", etc.. Better by the very high and hard won standards of our medium? Better emotionally?
So, I hope I didn't take up too much room here... obviously I had some Sunday afternoon time on my hands and photographic craft on the brain. Sorry I'm not the best writer, I hope the above was clear...