It depends whether you're doing a consumer facing site, a personal site, or a b2b site. Consumer sites tend to be better off with .com's. Personal sites and b2b have a little more wiggle room because you tend to link to them directly (as opposed to search). SEO is really what is comes down to though, if someone spells your company name (or how they think it's spelled) into google, will you appear at the top of the list?