as an owner of none of those mentioned above I can only offer input as to what I would purchase, were I to have the funds to do so...
Keeping in mind that we are a family of 2 plus dog. No kids. these are just my impressions as I have researched all three in depth, trolled the owners forums and spent time at shows in all three.
Toughness - Tvan by a tiny amount, followed very closely by the Vista RV, then the Ultimate.
Both the Tvan and the Vista are running very very similar suspension designs and I believe that Vista's parent company used to manufacture the Tvan chassis (though I could be wrong on that) It's not like I think the Ultimate is "no good"... it's massively in front of many (most?) campers out there currently. But against the other two... it's a close third.
Space - Ultimate first. then the Vista, then the Tvan.
Having sat in all three, the Ultimate has the most feeling of "s-p-a-c-e". It's just so airy and "open". But then that comes at a price. Setup time. next would be a tie depending on what you want in a trailer. The Tvan has the tent area, but it must be set up. While the Vista (esp the XL) has interior space with as good as zero setup time.
Comforts - this one is difficult... for me, the Tvan is perfect. But my wife now prefers the Vista. I'll call it in her favour. Vista first, Tvan second and Ultimate third. (basing that partially on setup time to actually access the comforts)
Setup time - Vista, then Tvan, then Ultimate.
for a couple, the Vista is just open the door, walk inside, lay down and sleep. The Tvan is next, but you need to open the tail pod and drop the deck, then the Ultimate which has much canvas.
Family friendly - well now this is where it all falls on its head... Ultimate first, then Tvan and then the Vista. Not actually *having* a family makes it difficult for me to comment accurately... But the upper deck space in the Ultimate, plus the option of the kids room underneath the adult bed makes for plenty of space. The Tvan's deck does provide lots of space as well, but the Vista would require swags or an Oztent for the kids.
End result - for us, (as in wife and I plus dog), we'd go the Tvan for what we want to do with it. (plus on the 2nd hand market, they're more in our price range)
However... if a Vista XL popped on the 2nd hand market at sub 30k, then that would suddenly become a much tougher decision.
All these thoughts are just my opinions and I'm sure actual owners of any of the three will set me straight where I may have commented poorly out of ignorance...