If I could only ever carry one type of call, it would be a mouth call.... You can get a wide variety of sounds in a very small space, and there is no movement... Versatile and relatively loud (but can be made to be quiet). Great call to use if you are going to "walk & talk" to sound like a moving hen. Very often when moving on a bird and trying to sound like a moving hen, I will use a mouth call while I actually am in motion.
Called in my first bird from start to finish with a scratch box (from Lonnie Gilbert) this season... I think they are a great call on the low end stuff, but you can still yelp, cluck, and cut on them... Perhaps because they are new to me, I enjoy tinkering with and playing them over other calls currently.
Box calls seem to reach out and cut through the wind... Easy call to sound good on that is fun to play.. Last year I had my daughter with me, and we got a distant gobble with the box... Figured it was too far away for much concern, so we had "snack-time" and played with our box calls... I was showing her how to cluck and purr, and just having a little fun with the calls... With our mouths full of peanut butter crackers, we suddenly heard gobbling almost right on top of us...
Three jakes and a tom (guess who was in the back of the pack)... They stepped right out in range, but would not separate. We were behind a log, and my daughter was thrilled to make little clucks and purrs to insight them to gobble each time she made a sound...