@INFJenNiFer it's definitely a question that makes me think. I think "Love what you do" involves a better mindset, or at least is less prone to dangerous misinterpretation. "Do what you love" has some assumptions built into it.
For instance, if you asked yourself, "Am I doing what I love?" you are assuming that there is something out there that you love. Contrariwise, if you asked yourself, "Do I love what I'm doing?" you may find yourself respond "well I don't love it, but it's pretty cool, and it makes money for my family, whom I love, and for me to have the free time to build trains, which I love," or whatever. So that's my reasoning at least.