UserVoice vs Zendesk

UserVoice’s simple engagement tools help you do more customer support and get more feedback in less time, without getting in your way.
Zendesk is web-based help desk software with an elegant support ticket system & a self-service customer support platform. Agile, smart and convenient. Zendesk free open-source alternatives are osTicket, OTRS, Mantis
Face to face in the news:

2013 - Zendesk for iPad - Built For Mountains to take on UserVoice

If you watch almost any promotional video about today's IT systems (for example the latest movie by Salesforce) - you'll see that people now work everywhere - on the street, in the subway, in the park, on the beach, in the woods, on the mountain, on a boat, on the snow - anywhere. Have you seen this in the real life? No? Me too. Zendesk (the SaaS service helping to support customers) makes fun on this trend. They released the new mobile app for the iPad together with the epic video (watch it). And the bonus (below): Harlem Shake (Zendesk Edition):

See also: How companies use Harlem Shake

2011 - UserVoice turns customer support into the Game to take on Zendesk

The average customer service worker hardly gets pleasure of his work. These stupid customers with their stupid questions or too nervous customers can make anyone crazy. Knowing this, the developers of helpdesk-service UserVoice used the game mechanics to make work of the support staff more interesting and their customers - more happy. In UserVoice support specialists play against each other earning points. For each response support person gets bonus, and if he responded quickly (within one hour) - points are tripled. And if the customer is satisfied with the answer, he may give the support rep the kudos that costs a lot of points. Boss may give an award to the support champion every week. Or may not, because this game is interesting itself.

It should be noted that except for this game mechanics, UserVoice is worthy of many kind words for the easy-of-use and functionality. In particular, it allows to easily embed on site (or Facebook-page) the customer feedback form. It can create tickets out customer emails and support reps can respond by email too. But it's more convenient to reply from the service interface - because you can use canned responses and communicate with colleagues to resolve problems collaboratively.