While .org stands for non-profit .co stands for Colombia.
Your website is probably not a non-profit and not colombian either.
I doubt any search engine would rank a .co higher then a .com when the same exact keyword is being targeted, unless you target colombia.
My advice is to go for a brandable .com or .net in your niche. It might take longer but it provides long term stability. Exact domains are perfect in case;
A: You want to take advantage of exact keyword matches.
B: Representing a brand for the exact keyword.
If you can't find the exact .com or .net then you can always try sedo and other ways to get that "perfect" domain.
If you have a good concept it's worth building a brand and spending more time to get those ranks.
Unless of course your doing a travel website on colombia.
PS: Wonder how many of you guys actually checked which country based google your websites rank on. I have not seen a single .co domain on number 1 for a decent keyword & would rather click the trusted .com, .net anyway.
Think bigger then quick rankings!