I’m not a martial arts guy, or in any other way all that experience in this, so what I’m about to say is just a guess. But I say it to maybe get the ball rolling since I’m interested in this as well.
By deep stance I assume you mean legs wider and body lower.
I think the pros are it makes you strong as a horse. It opens your kwa and strenghens your entire frame that much more.
The cons I would think are two fold. First, it’s probably easier to mess up your alignment in that pose, so you are more likely to be doing the form wrong. Second, since it’s so physically taxing, if you don’t build up slowly you are essentially turning a spiritual movement practice into a physical practice (i.e., you’re spending so much energy holding the physical stance that you’re not doing any of the energetic work).
Off the top of my head, those are my thoughts. Perhaps someone more knowledgable can chime in.