I did not include the basic functionality into the tables below intentionally, as its availability is obvious to users and does not require comparison. Functions that are not directly connected with tickets are included in a separate table.
|Bulk editing of tickets||Select multiple tickets>Press edit button. All fields available
||Selecting multiple tickets automatically opens edit window. All fields available except reply to user.
|Tickets by phone||Autoresponder with a separate number. Works in selected countries.||Manual input of conversation content|
|Tickets from chat||Proprietary widget, built-in chat from Zopim Chat, etc.||Proprietary widget and built-in chat from Olark|
|Ticket list update||Manually||Tickets are displayed upon receipt|
|Custom fields in tickets||Yes||Available in Next Gen interface|
|Text formatting in replies||Rich Text, Markdown||N/A|
|Supervisor in tickets||Implemented as СС field||N/A. Implementable with custom fields|
|File attachment||Only in user reply form||Available in user reply form and in separate ticket field for internal use|
|Getting client info from open sources||N/A||Intergration URLs|
|Client portal||HelpCenter and forum for chatting with customers||Yes|
|Knowledge base articles||Available only from client portal||Possibility to attach to ticket in reply form|
|SLA||Yes. Tickets contain time of next step. SLA reports are available.||N/A. Only creation of relevant rules.|
|Control of customer satisfaction||Yes. Possibility to display results in ticket list.||Yes|
|Rules of ticket processing||Constantly monitoring ticket changes||Divided into start conditions: upon creation, opening, change, by time, etc.|
|Adjustable work time||Yes, including holidays||Yes|
|Agent's time tracking||Built-in time tracking mechanism and third party apps. Time report available in constructor.||N/A|
In my opinion, despite the fact that Desk has its own indisputable advantages, considering the huge price difference as well as multiple red points in the above tables, Zendesk is definitely a winner in this case. You can check the review of the latter here.