I can tell you that it made sense for us as a company to use Kaviza rather than XenDesktop and also that it was an easy choice. As a hosted virtual desktop provider, we LOVE the cost-effectiveness of Kaviza, but we also love HDX and Kaviza is the only place you can get it outside of XenDesktop.
Also, because we have so many users running on Kaviza (5000+), we are getting really good at drilling our own API’s down into Kaviza so that we can ‘bend it to our will’ and in that regard it comes up higher on the list that XenDesktop any day.
To summarise, we chose it because of cost first (XenDesktop IS much more expensive), HDX second and ease of use/modification third.
Look at it this way too, how many awards did XenDesktop win last year ? You cant get in trouble for choosing an award winning tech when there is not much between them.
I am of course ignoring the most important point however, it DOES depend on your unique needs.