I have the one level below plus membership and I created two of my own personal portfolios. I can compare each portfolio using a basic benchmark such as a stock or ETF. However, I can't seem compare my two portfolios against each other. How can I do that or at least make one of my portfolios a benchmark?

There's currently no easy way to compare two portfolios. Probably, we can add an option to use one of your existing portfolios as a benchmark to support that use case. I’ve added an enhancement request to our backlog.