I can only comment on my experiences, which is with OKI Pro series and our Xerox DC250, DC12 and DC5252.
OKI printers will produce quality as good as the Xerox machines when they are new and all consumables are new. The problems come when OKI consumables are no longer new. Quality of print deteriorates once the consumables are about half way through their recommended life which means the only way to get the quality back is to replace the drums when they are only 50% used. If on a click contract, OKI will refuse to supply after a while as you will not be using enough clicks for the parts and if you are paying yourself, the costs per print make it uneconomical. Xerox supplies on the other hand usually produce consistent quality throughout their lifetime and will last as long as Xerox say.
OKI machines very rarely need an engineer call as most parts are user changeable. The problem again is that the parts will need changing before they are at the end of their life, which means the cost per print is no where near what OKI say if you want the quality. When engineers do come out, they expect the machine to be in an office, not a print shop and will say that the (poor) print quality is acceptable for the machine (yes, I talk from experience).
I could go on, but will just sum up. We had threaten legal action to get our OKI taken back as the quality was not consistent enough for pay for print. OKI machines are fine in an office, and maybe for a few proofs too, but once you start putting any volume through them, they cost too much to keep the quality good enough. We got a reconditioned Xerox DC250 for a similar price to the new OKI and the difference between the two was night and day.
