What is the best type of machine for making smooth nut butter? I want to make nut butter from soaked cashews or soaked pepitas. I am wondering what type of machine will get the smoothest product?

I am currently using a food processor which is great for cashews but I'm wondering if I can do better.  Other possibilities include a blender, nut butter machine, and some type of grinder (perhaps a wet grinder?).
Any machine that can reduce the nuts to very fine granules should do the job.

Wet grinders given there’s enough liquid/fat content in the nuts should do the best job. However that might not always be the case. Special high powered blenders (such a blendtec) with a purpose designed jar (like a twister jar) would generally provide more reliable results.