Hyphenated words in English usually undergo a transformation. They begin hyphenated and, as they become more familiar, the hyphen is lost. During the transition, both forms can be seen for a while. It is also true that AmE tends to lose the hyphen quicker than BrE. US speakers are generally more tolerant of neologisms. Because of this there may be long periods of time when different spellings prevail on opposite sides of the Atlantic.
The best strategy is to choose a particular dictionary (or a particular style-guide) and use whatever they suggest.
I agree with Biffo. I would use the hyphenated version because my Canadian English tends to lean more toward BrE than AmE, but many Canadians would not hyphenate it. Either will work.
I think Biffo's reference to words starting with a hyphen and transforming into unhyphenated can be illustrated by something we're all familiar with - I always write "e-mail" which is pretty-much the way most people wrote it when it was new. Now, however, it is almost more common to see it written as "email".