That is almost correct - if the com is not used then grab it. But I have few .info that I in first page on G since the .Com,net and org are not used or redirected. that said I do prefer the biz to the info
If you own both properties, then definetly use both!! One should be set up as your money site, and the other should help drive traffic to it. As for which one should be your money site, to me it all boils down to what you want to do with the site. If you are trying to generate leads or adsense income, then use the .info. If you are trying to actually sell a product or a service, then I would go with the .biz. Good luck!
i think .biz is better and if you bought both of them redirect one of them to the other one but why dont you buy a .com / .org / .net ?? they are better specially .com and the people love it more best regards