One's not louder than the other, you can broadcast on either a long or short box or play all the soft, quiet stuff, though I think getting quiet is easier on the long box.
The answer to your question is long boxes have more versatility. Across the rail of long box, you can kee-kee, yelp like a young hen, older hen, a jake, and gobbler, then change your hand position on the beaver tail and sound like different birds all over again. Then, switch rails and find even more birds all over again.
Here - this will help:
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