You were right — four times faster. I have downloaded the nightly and am now getting 40-60 fps on 4K content with my 16" MacBook Pro with M1 Pro. Remarkable. Mac Studio with M3 Ultra really is going to be scary fast.
Tomorrow I guess I'll test on my Mac Studio with M2 Max purchased in June.
Thanks!
UPDATE: As expected, M2 Max gets 50-70 fps on the same 4K content — ~15% faster, which is no small thing. That militates in favor of M3 Max roaring along around 90 fps, and M3 Ultra being truly terrifying.
It contains a fix for a stupid bug that prevented the VideoToolbox "speed" preset from working, and some preliminary support for the hardware decoders and some gpu accelerated filters. Try to enable them in the preferences, and play around with the VideoToolbox presets.