so for example my kw is curebackpain which is better of the two, or are the 2 good choices for domains?
I hope you already purchased them.....because they are for sure gone now! As far as your question.....which one had the most searches every month? If your keyword is cure back pain, then having it as domain name is best.
Steel balls is right. Go for both, why limit yourself when you're basically doing the research for both anyway?