From an SEO perspective, Google (and other search engines) really don't have a preference on the TLD.
All things considered otherwise equal, a .co or .net is not going to have less ability to rank than a .com. I suppose there are situations (as has already been mentioned) where country code level domains could affect whether they're displayed in a particular geographical area, but in general the TLD itself isn't really a ranking factor.
However, it is important to consider how the domain plays into user retention.
If visitors to your site tend to be typically through organic search and your primarily targeting new organic users versus returning visitors, I'd go with a domain name that's most applicable and choose an affordable, but reasonable TLD.
If instead, you aim to have generate most of your visitors through direct URL input or want people to return to the site frequently, I'd go with a more common TLD like .com with a relatively easy name to type in (no dashes).
The reason is pretty simple.
I have an ecommerce store where I sell novelty tshirts, for example, and most of my customers find me through search and I'm typically right at the top of the page. So they're finding me naturally through search with intent and that's half the battle and than I lock in a one time sale and that's that. There really isn't some gigantic need for them to remember my domain name because I'm not selling them the same t-shirt over and over again, they just want the one time product or the one time piece of information they searched for. In these situations, your page titles and descriptions are going to be the primary factor.
But I also have a web hosting and design business, and while people find me through search also, there's also this huge need to be able to mention a domain name on a business card, through conversation, or in a radio ad and suddenly the name and the TLD becomes extremely important. If you start adding dashes or go with anything other than .com, you're getting away from what people find is natural and if your competitor as the same name at .com as you have at .co, you could very well be driving traffic to them through those methods.