The thing I favor for Waves is that, not only do they painstakingly model antique hardware by brand, they go after specific units that have been used with great success, and simply allowed you to duplicate that exact device many times. UAD does the same thing, but where Waves has gone after specific favored units, I don't sense it would be wise for UAD to do the same as this would potentially compete with their hardware line of sales. Does UAD model their vintage equipment for plug-ins, or do they
believe the ones to model are the latest and greatest hardware offerings? I'm setting myself up to be contradicted here, but does UAD specify which exact unit(s) they modeled?
More, I agree with [yorolpal] in that Waves support has significantly become more customer-centric. Where some DAW makers don't study the ways of the plug-in makers, Waves knows the in's and out's of Sonar, and know how to work an issue to close without you having to conference in a Sonar support agent. Sure, Cakewalk cannot be help responsible for what Waves does to your DAW, but Waves support seems to know this demarcation.
I didn't care much for the WUP plan when I first became aware of it, but I will admire this about it. When sales are slow, and Waves isn't getting new products out the door in a profitable fashion, they don't suffer the lack of revenue they need to keep advancing or updating/fixing the existing plug-ins they already have. To be honest, if Cake instituted a reasonable CUP (like WUP), I would buy into it, because that would propose that Cakewalk could spend the extra time/effort for releasing patches, etc.
For Waves licensing, I agree that the licensing is tricky, and I read some Russian kid cracked it's security in less than a week, but I still think it's far superior to the ailing iLok technology.
For UAD, another thing to consider is the need for the PCI card. PC/Mac Hardware will almost always devalue and become outdated. You can't always trade-in the old hardware. That's what kept me away from the UAD, from the start, even though I had already invested in Waves.