I have a a 2,000+ lb Summit lathe w/DRO, a Hightower Deluxe and Unique's CueMaker lathe. All 3 have their purpose. I bought the "desktop" equipment since I was living in a rental home, but picked up the Summit once I had a more permanent location.
The desktop equipment will get the job done for cuebuilding. Like any tool in your shop, you have to learn how to tune it for accuracy. You can't go wrong with either of the two you're asking about. I can't say one feels particularly more rigid than the other, either. Just take cuts that feel appropriate to the task at hand on that machine. With a few modifications, you'll be happy with either one. In my opinion, the price difference is the main reason more guys have the Hightower than the Unique.
For me, there are a few drawbacks with both of the base models of the desktop machines. First, the handwheel's so much smaller than on the big lathe that accuracy suffers. That can bie fixed with an indicator or DRO on either of the two lathes. Second, both lathes also sell threading attachments now as well. And obviously, no heavy machining on either one.
I prefer to do my "hands-on" machining on ANY of the smaller lathes rather than the Summit, and I prefer the Unique for that. With their built in knuckle-saving chuck design, you can get get closer to the chuck than you would on any other lathe while finishing up tip work. There's nothing like working on an engine lathe; it cuts through the wood and phenolic like it isn't there. That power makes it much more dangerous, too.
Popular thought is to buy an engine lathe from the beginning. Pound for pound, a used engine lathe is a beter value. While I understand this logic and love my Summit, I'd never recommend it to a beginner. While the desktop lathes can hurt you, they are more forgiving. For me, there's a safety factor there that is often ignored. For people without machining experience, the cuebuilding lathes are the way to go - at least at first. If you outgrow the desktop equipment, you can always find another use for it later on. A number of highly respected cuemakers with enghine lathes also have a desktop lathe in their shop for certain tasks.
Best of luck,
~Beau