I haven't used many other email validation products before, only a couple of 'free' cloud-based options with limited list size capability. Kickbox is super professional, easy to use, and works.
It is great to use when a single email address is needed and for bulk leads as well. It has great integration with the third party tools that makes it easy to manage things and keep track of things. We can even generate campaigns through this.
I like Kickbox output files better as it includes the "domain". Overall, both softwares could do a better job cleaning lists. Kickbox shows more "unknown" emails where are BriteVerify shows less "unknown emails" but then more bad emails end up in the valid list. Kickbox has a higher threshold to put emails in "unknown".
I've used a handful of other products, one is called Hunter.io. Another is called BuzzStream. Both have their advantages. Hunter we've used as a backup to finding emails if VoilaNorbert can't find them. BuzzStream does have nice email finding capabilities, but they are also more robust from an emailing and tracking perspective. I know that VoilaNorbert has some of that functionality but BuzzStream's is more intuitive. But I think VoilaNorbert's email address capabilities are probably faster/better than the other two.