What is the best alternative domain name to use?

Im looking to set up a new website. Let's say the name I wanted to use for this new online business is ThunderReport (not my actually name, just 2 words I randomly generated to use as an example). However the domain "www. thunderreport .com" is owned by someone but not in use. I want to stick with the name ThunderReport.

I have identifed 2 possible alternative domains that are free, "www. thethunderreport .com" and "www. thunder-report .com". Which of these would people think is the best…

What is the best alternative domain name to use?