308 for mule deer.Fusion is a bonded jacket soft point, Whereas powershok appears to be a traditional jacketed soft point. The bonded bullet it less likely to experience jacket and core separation and penetrating deeper and losing less weight when expanding.
What caliber, and what are you looking to use it for?
Fusion should hold together a little better, but if the Powershok worked, and you were satisfied with the performance, I would stick with it, unless you cant find it and have the fusion available. IMHO it is a better bullet, but not a huge difference, and you only really need better if what you have is not meeting your needs, or you cant find what you normally shoot.308 for mule deer.
Used powershok before, never fusion. It is a bit pricier, and they market it for deer hunters.