I almost exclusively use a handful of rag-tag mouth calls that I make myself. They almost invariably get the job done for me and my general attitude is one of..."if they won't respond to my mouth calls, they probably aren't going to respond to anything."
However, twice this spring, I was getting no response with my mouth calls in an area I knew had gobblers close by. On one occasion, a buddy I was with that exclusively uses a box call got a group of gobblers going...and they came right in when I was getting nothing with my calls.
On the second occasion, I switched to a slate-surface pot when I was not getting a response when I also knew there were gobblers nearby...and they immediately started responding...and I eventually got one of them.
Being the "you can't teach an old dog new tricks" sort of guy, I will probably just stick with my mouth calls...but there MIGHT be times when I say to myself..."Maybe you should wise-up and try something different". ...Probably won't listen very often, though...