Just think of it like this - One of the Googlers used a great example in another thread.
If the name of your site is Experts Exchange.
Would you want:
One is clear, one sounds...adult
Another example, I'm just making this up, so sorry if it exists, but say it was about dolls and their looks:
One is clear, the other has too many of the same letters squished together and could confuse people.
Unless you run into the issues above, you could go either way, although hypenless would probably be easiest to remember (as was said, register both, have one re-direct to the other).