Last year Myers had a 91 Stuff+, 102 Location+, and 94 Pitching+. He doesn’t grade out well by stuff, but he located well enough and was able to effectively play his wide arsenal off each other (as alluded to in the Baseball America piece before the season)
This year Priester has a 98 Stuff+, 98+ Location+, and 95 Pitching+. He’s mostly a 3 pitch pitcher right now between the sinker, slider, and cutter. The sinker and slider are solid offerings by Stuff+, while the cutter is lagging behind
TLDR, Priester’s pitches grade out a bit better, but I wouldn’t say there’s a significant difference in stuff. Neither induce a lot of swing and miss and both are effective in different ways