No difference. ...... Okay of course there COULD be differences like that to 'some' people .com looks nicer. SEO and emotions sometimes are close to eachother, as a directory owner might place a .com domain on top, because he would fancy that domainname more than the .net one. But thats just promille chances. A better .net domainname > a less good keyword .com domainname (if you only think pure about SEO)
It would make a difference if the TLD is one of your keywords. I.e. for a site about Microsoft's .NET framework, you'd get a bit better ranking in the SE's from having your TLD as .net. Proof: http://www.google.com/search?hl=en&...official&q=allinurl:dinosaur+info&btnG=Search 10th result: www. cuddlyfuddly.info/dinosaur-toys.php --- google bolds the .info part of the domain name, showing it ranks the site higher because of the keyword being "inurl".