"Toward" or "towards"?

The Common Errors in English Usage site mentions:

These two words are interchangeable, but “toward” is more common in the US and “towards” in the UK.

Some people, probably influenced by “forwards,” write “torwards” instead of the correct “towards.”

The merriam-webster simply list both words under the same entry, with similar ethymology:

• toward: Middle English toward, from Old English tōweard facing, imminent, from tō, preposition, to + -weard -ward
• towards: Middle English towardes, from Old English tōweardes, preposition, toward, from tōweard, adjective

Despite the trend that "toward" is more common in the U.S. and that "towards" is more common in the U.K., I still see quite a bit of inconsistency within the same country, within the same publications.

For example:

The New York Times with "towards":
nytimes.com/2002/08/31/opinion/slouching-towards-9-11.html
"Slouching Towards 9/11"

The New York Times with "toward":
nytimes.com/2010/02/04/world/europe/04tuna.html
"Europe Leans Toward Bluefin Trade Ban"

But for the most part, the Times seems to dominantly use "toward", and then "towards" when quoting a British interviewee, which further supports the claim about the geographical distinction.

I suppose either one is fine as long as you're consistent.

I'd say they are interchangeable. I've stopped using "towards" altogether and started just using "toward." It definitely is smoother in sentences.