The power of domain names in google does not matter all that much.
However for resale value follow this guide.
.com > .net > .org > other TLD
In some cases this is varied, for example is you have a hack (drivesafe.ly for instance) they can become much more valuable than any others.
However, for the money spent, hit the .com then the .net. If they are both available, take both, as you may get ghosters on the net and org TLDs.