Eg if you build abc.com and abc.net and abc.co at the same time, which one will be listed as preffered on SE's result page? I know .com will outweight .net and .org. But not sure about .co.
i dont think anyone has a concrete answer. the co extension is very new - and it all depends on the mass majority of people will start using .co and not enter .com as many are used to doing
Search engines does not care what extention you are using... as far as I know, the only ccTLDs that globally target are .TV .CO .ME
But I think it come to consideration as well when or how you want to promote your business. Correct me if I am wrong. But .com is mostly used for to target US traffic? and that .co will be for columbia traffic??