Agree with everything said on the XRV750. Great bikes. And wilbjr21 did a really good summary of weak points.
The only thing I'd add is that the Nissins are made of alloy...cheese and crumble at the sight of our well-salted roads. Second-hand supply is dwindling, but some Transalp callipers fit. They are also really popular in hotter climates, so ebay.<somewhere south-european> is a good bet.
Be aware that they are an "appreciating classic", meaning that some parts are out of production and some are hard to find. My selection criteria would be the output shaft condition and then plastics (as they can't be bought new any more), everything else can be sourced and it is a pleasure to work on. For completeness, you can get an output shaft, but that is a major (case-split) job that I wouldn't fancy and I did a complete resto of mine.
Not had the pleasure to ride the new AT yet, but admiring from a distance so far with the second hand prices out of my range... That said, did you drop your one off yet @Smartbazza? That was /is one serious temptation...