It's my opinion that louder is not necessarily better. I'd wager that most people call too loudly, and they also call too much. I'd also say that clarity and sound quality are far more important than actual volume. Nobody other than PredatorSpanker can really comment on the Loud Mouth, because they're not available yet. It does look like a great product though. We'll just have to wait and see.
I know for a fact that the Foxpro is plenty loud. I unboxed mine in my car, not knowing it had batteries in it, and turned the power on. It nearly busted my ear drums!