I’m no authority on the matter, but from what I gather, Kifaru tends to discontinue items that aren’t strong enough sellers. Being that the Urban Zippy isn’t a hunting pack, I suspect it falls under the category. They’ve discontinued many items that many still strongly desire. Not just bags themselves, but even various attachable pockets or awesome patterns like Typhon and Highlander. It’s beyond me why even some colors are discontinued if the bags themselves are made to order (but sewn in batches). I know some say just keeping the extra fabric around is too costly. But again, that explanation doesn’t really compute for me. There must be other reasons.
You are correct that the Urban Zippy and X-Ray are quite different packs. I have both of them. I actually never thought them to be comparable; other than they are both not big bags. I love my Zippy for my EDC around the town, amusement parks, etc. I love the external integrated side water bottle pockets and 500D material to keep things light as possible. If you carry a lot of loose/small items, they can definitely fall out the sides of the Zippy if you’re not careful opening. Easily solved with pullouts. (I recommend the ultralights). But I do love those side internal mesh pockets....so handy!
However, if your bag is going to see some abuse and/or you want to carry more/heavier gear, you might want to go with the 1000D X-ray. You can’t go wrong with it; quality is awesome. It is 500ci more though, so just more bag to haul around. If you’re going to utilize that space, great! But I prefer to stay as small as possible and limit my gear to everyday carry.