Paper or plastic?
You're clearly a wiseass, Nick, but I do admire your brevity. I'll assume, charitably, that you're not just flinging linguistic poo at the answer monkey and you really want an answer to your question. That answer is: It doesn't matter.
As a Portlander and a WW reader, you're more likely than the average American to be aware of the well-trodden calculus demonstrating that paper vs. plastic is a wash: Paper is easier to dispose of, but more energy-intensive (and polluting) to make. Plastic is light and carbon-cheap to transport, but is functionally immortal and rarely recycled.
This Scylla and Charybdis of the checkout aisle is, of course, the reason that bringing one's own bag has recently started catching on in a big way. Surely that's the real answer, right?
Sure, go for it. But the main problem with the paper/plastic conundrum is that it's gotten so much press (ahem) that you'd think it was the most environmentally consequential decision you can make in the grocery store, when in fact it's not even close.
Are you a fan of bottled water? It costs twice as much in fossil fuels as our grocery-bag habit does. And if your reusable eco-bag contains, say, a 5-pound beef roast—well, you might as well just drive your Hummer to Al Gore's house and take a dump in his mouth, because that one chunk of meat burned more crude oil than a year's supply of plastic grocery bags.
Other things that would make more of a difference than bringing your own bag for a year include carpooling for a week, buying one compact fluorescent light bulb, and roasting John Boehner in a solar cooker. By all means, use fewer grocery bags. Just don't expect to save the world by doing that and nothing else.