So the summary is that a longer message has a higher chance for a response, but it's more efficient to just spew out a lot of shorter messages and spam everyone.
Short introductory messages are, however, useful for screening out people. After that you can go long. Even with a narrowed down pool, you're wide enough that being able to message the entire pool rather than a subset should be the more effective option.
Frankly, this is pretty close to link bait in my book (hot topic, no substance)