For me it really depends on what I am in the mood to read, and to some extent that depends on the forum. I don't pick up a newspaper to read long prose. It just doesn't "look" right, and that's a turnoff. If I pick up a paper, I don't want to look at 4-inch-long paragraphs. Tires me out. I want a quick read. Get in, get out, let me go on to work. Don't make me trudge through 60 inches that could have been 30 or six-sentence paragraphs that could have been two.
If I am looking at a magazine, I am in the mindset to read something more substantial. The format does make a difference for me.
I field calls every day about stories our writers have crafted. They've put in the work, written what they think is a great 50-inch piece of prose. And in most cases they're right. They are very good writers and my shop is definitely known and praised often on this board as a "writer's paper." But the calls I get are not usually, "great job, wow, I was moved." It's usually, "nice story but it was tooooo damn long."