And the 285H is lower performance than a 275HX.

Their laptop naming scheme at least is fairly straightforward once you figure it out.

U = Low-TDP, for thin & light devices

H = For higher-performance laptops, e.g. Dell XPS or midrange gaming laptops

HX = Basically the desktop parts stuffed into a laptop form factor, best perf but atrocious power usage even at idle. Only for gaming laptops that aren't meant to be used away from a desk.

And within each series, bigger number is better (or at least not worse - 275HX and 285HX are practically identical).