Article length....

^^^ This.

In fact, you don't necessarily need an article attached at all, just to get a backlink. And there's certainly no particular point in having a long one, if it's for "backlinks only", because it's going to be seen only by search engines, not by people. So most of the "usual arguments" about article length are completely irrelevant to those situations.

But the valuable backlinks you get from articles are from context-relevant authority sites, of course (just like any other valuable backlinks). And you're certainly not going to get (m)any of those with short articles, because of the reality that almost nobody wants to syndicate short articles.

My articles are typically 900 - 1,200 words - sometimes a little more.

Over the year that my articles went from 400 to 1,100-ish words, my CTR gradually declined and my sales gradually increased. And they continue to, mostly because my longer articles (unlike my shorter ones) get taken from article directories and widely re-published. Other people are doing some of my off-page SEO for me, in other words, and in front of targeted audiences, too. This is where the real money is, in article marketing. In all my niches, apparently.

Some people think that "shorter is better" because "most readers have a short attention-span". I think this a huge fallacy. I'm sure it's true, but it isn't actually relevant because they're not the ones who buy: they're the larger numbers of readers I don't mind losing for the sake of attracting a few more buyers by giving them more in-depth content. That's what all my sales figures are telling me, anyway.

I think all those 250/300-word articles one sees in poor directories are knocked out by marketers who have bought in to the nonsense about it being advantageous to have your resource-box "above the fold". These are mostly people who haven't tested properly, but just believe what they're told by others who know no better. They're typically measuring "clicks", not income. They characteristically assume that anything that increases their CTR is going to be good for business. (This is a deeply mistaken assumption!).

Some reasonably longstanding, closely monitored, well tested experience over more than a year in 8 different niches has shown me that if I use something like a 1,000-word article instead of two 500-word articles, I'll consistently make considerably more income from my work, even though the total number of backlinks I'm putting out there myself is initially smaller.

For some purposes, size really does matter.

Depends on who or what you're writing for. In general, I don't bother with anything below 400 words. I generally try to keep mine between 450 to 600 words for good measure, especially if I'm promoting a product or service.