@Benjamin Ellis it depends on what type of owners you're contacting.
Looking up individual phone numbers and calling owners is super time consuming, so I only do that with owners I have specific info on that makes me think there is a high likelihood they'll be motivated. For example, I do think it's worth looking up owners of vacant houses and trying to call them because if you can actually get in touch with the owner of a truly vacant house they are probably the most motivated sellers of all because they have no interest at all in their property any more.
Another prospect it makes sense to lookup phone numbers and call directly are pre-foreclosures.
One service I'd recommend for finding phone numbers for vacant owners, but it ain't cheap (about $300/mo) is lexisnexis.
If, however, you're targeting owners with lower likelihood to be motivated, like high equity home owners, which I do also, it would make no sense to call the owners because 19 out of 20 will have no interest in selling and/or be asking way too much for their house. Those people should get letters.