This is mainly my observations and I'm putting it up for later use but I also thought it may help artists a bit too.
I've noticed an uptick in the pits and bullies on here for a while so this could help anyone who gets stuck on it like I do.

bull terriers have a bit of a 'cheetah skull' shape, only their eyes are smaller in relation to their head.
where pitbulls are more like tigers and jaguars with a broader, heavier muzzle and head/cheeks, and much more jowl-y.

their much more compact then wolf heads. Bullies hold and crush, where wolves snap and catch. Think feline, and more trapezoidal shapes. Heavier necks are also a good thing to practice.

This isn't a definitive Guide by any means but hopefully it helps someone in the confusion that often gets me.
(will put in scraps later) let me know if there are others like this I can do.
art©   lavasi