I go with word counts because page counts are so easy to manipulate (font size, page size, font type, spacing, etc) – I remember playing with those back in school when a teacher would specify “X” pages and I’d come up otherwise short.
I’ve tried 3Kwords, I’ve tried 25Kwords, and I’ve settled on a general rule of thumb for 6k-8k. However, I’ll tolerate less/more if the chapter/circumstances demand it. At 10k I’m generally looking to see if there’s a good way to divide it. Below 5k, and I’m considering whether the chapter should be condensed with another, or something should be added. Too short, and nobody gets engaged to click that “next” button, and too long, well, both makes it more daunting to me as an author and gives fewer natural “resting points” for the reader to set aside and come back later (I mean, if it’s a really long story, they need breaks).