OK, I had heard about it, I just knew of it as the 25-243 or 25-08...just hadn't heard of referred to as the 25 Souper...the more I research this topic the more questions I have for myself. From what I have determined so far the 25AI may well have an advantage, all be it a slight one, over the 25 Souper...mostly due to it being more common (load data, dies, etc...) and velocity and accuracy are comparable from what I have found so far. At the end of the day my 25 WSSM probably competes well with all of them. That being said, I still want a to build a custom rifle, still leaning toward a 25 cal...and the 257AI keep coming back...but until I find my donor rifle, I can keep on thinking anyway...hahaha! This build is my 10 year anniversary gift from my wife (pretty nice wife huh?).