So I was wondering if people felt the same way as me regarding the length of reviews. Personally, I prefer short ones, just a few sentences. Basically, if I am looking for a movie to watch I'm not willing to read through a whole "book" of text, which tells me everything about the movie I am about to watch. Plus, if I am going through reviews on sites such as Rotten Tomatoes, I tend to automatically skip the long ones and just read the short ones where the person's opinion of the movie is nicely said in a few sentences.
In most cases, I prefer short ones as well. I strive to keep most of my reviews to under 700 words. I find that most writers who submit reviews to my site have a lot of trouble keeping things short and sweet. Writing concisely is a difficult skill to master.
Longer form reviews should be more reflective essays, and address/expand upon some larger theme brought up by the movie. Longer reviews are generally read by people who are already fans (or haters) of the movie and are looking for more insight, rather than people looking for recommendations for something to watch. Two different audiences.