First things first both are having their own merits, however in my personal experience ZAP can replace your burpsuite for sure considering the License. Also as the latest ZAP versions are covering more advanced techniques and spidering patterns with lots of options in it, it is worth considering ZAP. However remember that burpsuite from latest versions with inbuilt chromium and it's emerging plugin support (Installable jars) you can use burp to the fullest and you can keep it as a swiss knife for your web and app pentesting. Couple of extensions in burp pro are interesting especially the race condition one. I always prefer using Burp and at instances I go with ZAP.
I work as a Software Test Engineer, designing and executing test cases according to clients' functional specifications.
I am currently evaluating OWASP Zap and Qualys. What are the main differences between the two? Which would you recommend and why?
I appreciate the help. Thanks!