Without if it is available, otherwise with hyphen will do as well. This has been asked quite a few times, a simple search would have gotten you the answer instead of a new thread.
The domain name with hyphen should be secondary, even in case you go for hyphen don't go for more than one hyphen.
definitely without would be better ... but if u expect ur site to be popular .. get the one with the hyphen too ..
I always recommend to new clients that we go without hyphens whenever possible. What's slightly interesting is that I find most people prefer having hyphens over not. That's probably because they're so concerned with readability of their business name.
without is going to be more brandable, espcially offline... when you tell someone that your website is "whatever.com" instead of "what -hyphen -ever .com" for example. If your name is taken then a hyphen version could be your next choice but you could lose traffic to the non hyphen version.
People may hate em, but I sold a Loooong one last year for $850! auction-resource-alerts.com 21-letters, 2-hyphens, and I STILL had a pr-4. Pete