It depends on a few factors.
1) How natural does the chapter feel to you (and, if possible, to a beta reader).
2) How consistent is your chapter length going to be?
3) How frequent are your uploads going to be?
If the chapter feels natural, then irregular lengths might not be noticed by most readers. If it does not, they will get upset, and more likely over shorter ones than longer ones, but both CAN happen.
If you update frequently, shorter chapters (<=1K words) are far less likely to tick off readers; if twice a week or less, you probably want to stay between 1K and 2K.
Readers prefer a consistent experience and seem to think it happens more often with shorter chapters released frequently or medium length chapters (1200-1500 or so words) dropped regularly, but really, just provide them a consistent experience and, if possible, a warning if for some reason you go "out of range" - either too few downloads, or a chapter much longer or shorter than usual.