FWIW I set up a prototype risk/reward metric to help prioritize between various fund choices - for learning, like you. The risk ratings are a composite of leverage, discount/premium, Z-Stat, and NII dividend coverage. Each factor rated from 1 lowest to 4 highest in risk.
- For reward, it's absolute distribution % on NAV (not price).
- Then reward to risk is: NAV D% / composite risk.
- Ranking the reward to risk, invest in the highest ratios.
Ex: PDI has the highest "risk" at current because its premium has spiked back up to 9% and its NII div coverage is just "fair". With its top-of-class yield on NAV currently at 15.1%, my (cute and probably inaccurate) metric is a 1.7 risk/reward ratio. PHK has 2.1 because better NII coverage and lower leverage with a 12.9% yield.