I like a mixture of lengths, for writing and reading. If Medium had a 150 word limit, I would find that frustrating.

Shortform can be good for a quick bite, but it lacks depth. The key to good longform is to make sure it's well-written with no fat. Not loads of boring waffle. For example, Jared A Brock's 21-minute read crammed full of writing advice. It's solid gold. At no point in reading that was I wishing for it to end.