I think this URL is better race-car-test-driver(dot)com because it can be read as seperate word. But ranking can also be depend on your optimization.
It's pretty simple to test whether domain name helps or not. Do a .99 cent test. Go to Godaddy, and register a .info for .99. And make it in a niche that doesn't have all that much competition, or a regional niche. And optimize it in every way On-site that you can think of for a different term than your domain name, and then see which one ranks higher. You'll see that google will give you a high ranking just by having your domain name equal to your keywords. The simple fact is that google likes it, whether we want to admit it or not. It's the most important "on-page" factor for google that you can find. I didn't spend a whole lot of time pulling up relevant examples. But, look at for instance used cars atlanta or auto insurance atlanta. In particular notice the website www.autoinsuranceatlanta.com. That's in a market where the PPC players are paying over $10 a click. And they rank in the top 3 with a PR of 2, and just a handful of links coming in, plus a Yahoo Directory listing. I know this works, because I have seen it myself. I took a regional niche client. Took a website that was on a vanity domain(ie the company name). And then put an exact replica of the website on the domain that was the keywords they wanted to rank for. No other changes because I didn't get to it yet. And after google indexed it, they were ranked #2 of 1.2 Million results. Compared to the previous website that had been around for two years that ranked around 400 or so. Easiest SEO I ever did, and cost the client about $100. But like I said, try it out yourself, create a .99 website and see what you can rank for when it really doesn't matter. MR