I'm a long time AdWords user and just started doing a test with Facebook a few days ago. Initial thoughts:
I'm diving more into it later today so if anything else jumps out at me I'll comment on my post here.
My recommendation (which sounds like what you're doing) would be to test Facebook and see how it performs with your AdWords results. And also to educate yourself, which you're obviously trying to do here. I took a crappy image, cranked out my ad creative in a few minutes based on the verbiage for my AdWords ad creative and ran with it. Even at that, I was surprised that it started performing almost immediately. (We track visits plus customer sign ups based on the source.)
I'll be interested in other answers to this too because I'm sure I can get much better performance in terms of reach and I hope on costs.
Put yourself in the user's view, and try to come up with the use case to justify your investments.
I once read a statement from a senior executive (senior in terms of career and age) who said "Facebook? Yes, I use it to see my grandchildren pictures!"
What this means is that this grandpa, which might be a good target for your product, is in fact using Facebook. But when he goes there, his mindset is not to "find a product to buy".
He goes there to connect with his family! Wrong place to pitch a product... unless it's a special offer for discounted toys that grannies can buy for their loved ones...
On the other hand, if someone is on google searching for something, and if your product has a match with the keyword he used for the search, there's a good probablity that your product might interest him.
He's mindset is "I'm looking for something". He may not want to buy it just yet, but he is definitely looking for something... if that something is your product, you have a match and a potential prospect.
This is especially true for B2B. B2C products have some more probability of justifying an ROI on Facebook...
To do what, exactly? What is your purpose behind the purchase of these ads? Are you selling something? Are you attempting to generate web traffic? From our experience, Google ads work well in selling business software. Facebook ads do not work at all in selling busines software.
You might see different results with consumer software, or in just driving web traffic.
In general, people go to Google to look for things, people go to Facebook to socialize. So I would expect that Google Adwords would be a lot more successful for selling most types of products and services. But I only advertise on Adwords, not Facebook (ads for software used to be banned on Facebook), so this is just supposition. The one possible advantage of Facebook I can see is that they have better demographic targetting (e.g. by age) than Adwords.
I don't have any evidence to back this up - but my hunch is that when people are on the lookout for something specific and see something that looks like it will provide an answer, they will investigate it no matter where they see it, as long as it seems reasonably credible.
I have clicked on FB ads that seemed relevant to me. I haven't yet made a purchase because of them, but I think that's more because of the quality of ads on FB in Australia at the moment.
So I think FB ads could work, but more because they come across people's peripheral vision and look like they will meet a need rather than because they are searching for it directly at that moment. (Can't beat Google for that.)
However, the key (as with everything on the web) is test, test, test.
I have tried both. And I can say that Google adwords are better in terms of hitting the target you want. Facebook ads is too expensive and your ads will most likely clicked by young teenagers that do not have interest with your product. I quit using Facebook ads knowing the facts that most Facebook users that click the ads are young teens. In terms of ROI, I would say you get better value with Google adwords.