Firstly, I would think about it across entries rather than just singular ones. If you have a lot of different experiences, then you’ll want to keep the entries generally shorter as collectively there will be much more to read through. If you have fewer experiences, you might want a little more detail. Basically you want to get the balance between providing enough relevant detail to sell your experiences without it becoming too long to read your work experience in total.
It also depends on the experience itself though. A couple of days work shadowing may only need 60-80 words, while a paralegal role that you have done for a year where you have had varied responsibilities might need more like 250-300 words.