What's better sonicWall or FortiNet? and Why?

Fortinet having always complain Limited inspection capabilities, poor performance, Un-optimized Hardware platform and invisibility of application in their Fortinet 

But in Sonic Wall we will never face these problems, SonicWALL is Better

 Poor Anti-Spam Options – The FortiGate email filter service is limited to three dynamically-updated techniques (IP Reputation, Message body URL check and Message body content signatures). SonicWALL Comprehensive Anti-Spam Service utilizes 3x as many techniques including those.

 Basic Application Management – SonicWALL's running SonicOS 5.6.4 and later with Application Intelligence, Control and Visualization provide a comprehensive set of application management capabilities. FortiGates are limited to very basic allow, block and log. Also, SonicWALLs have 3x as many application signatures as FortiGates. Costly Central Management – You will need to purchase and run FortiManager and FortiAnalyzer together to get the equivalent features of SonicWALL GMS.

No IPv6 or ICSA Enterprise Firewall Certification – While FortiGates may support IPv6, SonicWALL NSA and E-Class NSA Series appliances are IPv6 certified. In addition, SonicWALL is the first network security vendor to receive ICSA Enterprise Firewall certification. Fortinet products have no such certification.

it was difficult to say who is better than one, and the question didt specify which type of FG or sonic wall in comparison

but in generally i recommend now using palo-alto or Cisco source fire instead of two   

and if i put in charge to select one of them i will choose FG based on Gartner report in Q4 in 2016 

Fortinet has good User Interface, Web filtering and ssl inspections which so good. Sonicwall adds little complexity creating these but my upvote is for Fortinet.