What is the most efficient way to compare similar contents in two lists?

[Zachary Dziura]

For this script, it's guaranteed that whatever tables the script goes
through and processes, there will be no duplicate headers. I didn't
include functionality to deal with duplicates because there won't be
any to begin with! I just wanted to find out the most efficient way of
checking for similar headers, which Chris A. told me! Thank you again,
Chris! You saved me a lot of headache!