money
With nonfiction, anything under a quarter a word is on the low side, but anyone who won't turn on a brain cell for less tha fifty cents a word is going to have a limited supply of magazines. There just aren't that many out there, and they're such a diverse lot that one writer isn't going to have the expertise to write for too large a group. Most such magazines already have nearly a full stable of writers, and breaking in is difficult. As for dollar a word or more, last time I counted there were only 89 in existence, and not all of these are open to freelancers.
But the truth is simply that anyone who writes short stories for the money is going to have a rude surprise coming, especially if they think about it on a per word basis.
There's a lot more to consider than how much you get per word. One big consideration is how long it takes to write something, and the odds of selling it. A nickel a word story written in four hours gives a better hourly rate than a fifty cent per word story that takes fifty hours. It always works better if you break income into hourly rates. Of course it does work the other way around on occasion. I've sold stories for a nickel a word that took weeks to finish, and I've sold stories for fifty cents per wrod that were in the mail four hours after I got the idea.
A bigger consideration is that initial payment is not where any good writer makes his money. Whether it's a penny a word or a dollar a word, the real money is made from reprint rights, collection rights, and anthology rights. This is true of fiction and nonfiction. Over time, these can dwarf any initial payment. This means that while it's best to sell for a higher word rate, just about any sale for any amount has the potential of earning the writer a lot of money down the road.
The best use of short stories, however, isn't for the money, it's for the publicity. If you also write novels, short stories published just about anywhere for any word rate can still draw in a lot of fans who will buy your novels. This is often worth far more than a dollar a word.
As for print versus web, there's no real competition there. Print magazines are in trouble largely because of how distributors handle them, and because the price of paper is so high. Many print magazines also have electronic versions, and it doesn't seem to affect sales of the print version much or any at all. The real problem seems to be that not many people want to pay for genre short fiction, whether it's print or electronic, and it's this that is causing trouble for many electronic magazines. There are plenty of webzines out there, but precious few that make a profit.
I seldom write for any magazine that pays less than a nickel a word, but only because I don't have to. I usually sell a story before it hits magazines that pay too little. But if a magazine pays at all, and if I have no other market, I'll gladly sell to it because the real money is in reprints, collections, anthologies, and publicity.