Well im sure theres many pros and cons but the ones i have noticed is a croutch type fighter is much harder to hit especially if you tend to head hunt whereas a square stance leaves you more open to a lot of attacks i know personally when i fight someone whos upright and square im gonna go low for the solar plexus with jabs then switch feinting low and hitting high so someone with a lot of variations of good strong jabs is going to be a problem which is almost every fighter, a square fighter has his right hand in a greater position to use i suppose but still on the inside it all changes anyway and even a croutcher will opt for a more neutral stance to utilize his right hand more while hes in there. i agree with what coco said you need to experiment yourself and youll find what your comfortable with for me it was always a crouch i tried to change my stance when i first started boxing but just kept going back to what felt natural, if youve already been boxing i wouldnt suggest trying to change your style, i could go on and on about pros and cons but i think it all really boils down to that.