It depends on context. In general, I like one-word .COs more, but it depends on a number of factors:
1. Brand vs. Info
Is the emphasis going to be on the name functioning as a brand (.CO) or on an informative site that's "about" the keyword (.info)? In other words, I see .info as more literal. Butterfly.co could be a brand for any type of business, whereas at Butterfly.info, I'd expect butterfly-specific information.
2. I don't love plurals in .CO
If you ask me, Computers.info sounds better, looks better, and is a more valuable name than Computers.co. (But with the singular, Computer.co would win out, and would be the name I'd want to own).
3. If it's to resell, are there end user sites in the targeted industry, using either of these extensions?
If it's a startup, .CO.
4. It might depend on the region.
.Info is older and more widely used in places like Germany. German Generic .info sales far outpaced English generic .info sales by several tens of thousands of dollars, at least a few years ago (second to .DE, of course).
I tend not to handreg .COs and .INFOs. If you stumble across a good non-plural .CO that isn't taken and that fits the profile or something that would sell, take it. But in general, names in these extensions that are going to have some value will be found in the aftermarket.
Personally, I would opt for choosing neither. If not .com, then .org if appropriate.
Edit: Got me thinking if names ending in co and info did better in .com than .info and .co. I checked namebio, and clearly .co and .info did better than the latter. The sale prices on the top 100 .co are higher than the equivalent .info sales, plus of these large sales .co seems to have about a 5 year old sales average, while .info about 10 years old. Based on that, I would say .co is the way to go.