Ultimately you can’t tell which type of policy will give the highest return on investment. A variable universal life insurance policy is invested in the equity and fixed income markets. Potentially the rate of return in these markets is much higher than the rate of return on a whole life insurance policy. As anyone who has invested in the stock market will tell you, it does not do with without risk, or ups and downs. The marketplace is risky, and even a high performing portfolio experiences the peaks and troughs of bull and bear market cycles. Some people may deem this risk too much for their life insurance policy.
Similarly a universal life insurance policy may end up outperforming a whole life policy depending upon interest rates. A universal life policy will adjust to interest rate changes more quickly than dividends adjust, and potentially either return could ultimately be greater.
A variable universal and universal life insurance policy also have other benefits, such as the flexible premium payment structure. You can add in extra money if you want to take advantage of your life insurance as an investment more than the planned premium. You can also not make payments for periods of time and let the insurance charges be paid from cash value. These benefits have value beyond participating in the life insurance companies profits.
When you account for the safety, stability, and tax advantages, a participating policy is often the best choice for many people who are not best suited for term life insurance.