Rule of thumb for me is always secure the .com I've used both many times and found no advantage or disadvantage with regard to SEO. I never base my actions on SEO as it's such a fluid science that changes in a major way about every 6 months. A .com is always best. A .co will give you a startup/tech appearance as will a .io domain.

One thing you get with a .co are tons of perks with partner companies, events etc....they really have some great perks unlike so lesser user perks programs like for example found on klout.com