I've shied away from shorties, thinking there's a big power loss. Just found this chart on a thread here. The power difference is not so much at all, not only between shorties and full tubes, but the gains over manifolds is shockingly small. It may be that the gains are a lot more when you get into the 400 HP range I'm shooting for.
Of course who knows how accurate the article is but the numbers don't really look like they are intended to sell anything in particular.