We print books on Oce, though color is done through Xerox.
It sounds to me like Oce would be a good choice for you. I'd have to disagree with earlier posts saying that there isn't a quality difference between Oce and Xerox. The newer Nuvera (emulsified toner) seems to me to have exceptional quality which is superior in every way to any competing machine on the market.
For training manual level quality, the Oce will be more than sufficient. Really if you're keep up on the maintenance, Oce should be fine for anything that isn't a black and white art book. They undoubtedly are very productive machines. I would suggest, however, that you should be sure to print a long run of a few of your books through both machines sticking as close to your final production process as possible. There were hidden "gotchas" in both machines for us.
For the Oce 6250, the RIP often had serious trouble keeping up (we do POD, so this might not be an issue for you if you print short run). The Oce also has a regular cleaning cycle that they don't tell you about which will slow you down -- the speeds they quote pretend that this cleaning cycle doesn't exist. The cleaning cycle wastes about 30 seconds everything few minutes -- exactly how long depends on a setting on the machine.
The Xerox RIP is dramatically superior in my brief experience, but we were slowed in another way during testing. They recently expanded the max sheet size for the Nuvera, which was very nice for us. Unfortunately, they didn't change the image drum size when they did this, so going above a certain sheet size (I don't remember exactly what) scraps a usable frame from the drum and this drops the production speed by about 30%. I don't think this affects SRA3, but you make certain.
Never believe the marketing. I'd schedule a demo for the morning and bring your own paper, because it seems that if you depend on the demo room to get things right then they're always running a little short on paper, and the introduction from the sales guy always takes a bit longer than expected so the demo room is closing soon. Test, test, test. Don't believe anything you're told until you see it yourself and make sure that you will be able to see everything you need.