I like constructive criticism, although I'll never turn down glowing praise. I might blush a little, but I do like it. What.s really, REALLY useful is knowing what worked for readers, and what didn't. My editor was all bothered by one review on Goodreads, where the reader felt I could have done more character development in my debut novella. And you know what? That reader had a valid point. I don't see that as a negative, because it tells me what I need to do better. The reader did go on to say that they were looking forward to the second book. Let's hope I did better, but if not, that's still valid from that reader's perspective, and I'm not crushed to be told that.
I don't worry so much about long or short, or if it's one returning reviewer or many reviewers. When I write online, either is fine. When I publish, I get one shot at a review, so it's not an issue.