We started as a .co A while after we bought the .com Now we are considering if we should change everything we've built to the .com domain Are there any benefits in terms of SEO or similar?
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