Question about Git and branches for experiments

Following up on a prior discussion about Git tutorials vs. workflows, here's a question about Git workflow in a particular situation:

I am working on a project that involves evaluating two different libraries for a specific function. I have it implemented with the first library, and am about to implement the code to use the second library.

So, what are the relative pros and cons of using branches vs. cloning the code? Is it simply a matter of preference? When is one approach preferable over the other?