The downside is that the incentive fees get much more complicated - too complicated to lay out here. I've modeled the scenarios in the following Google Spreadsheet (feel free to copy and play around with this): https://docs.google.com/spreadsheets/d/1RlB4iwg42dEa-atdti4H...
If you do check it out:
Notice that in the [high ret] scenarios, there's little difference in total fees charged between the "fair" 6% hurdle and the 2-and-20 scenario. However, in the [low ret] scenario, the fee difference can be quite substantial: $227k for 2-and-20 vs $70k for the 6% hurdle scenario. And the resulting
Please feel free to copy and play with the values if you'd like. I'd love to discuss in more depth.
The 6% hurdle is a reasonably fair expectation of annualized stock market returns going forward for next 10-20yrs. If there's sufficient interest please reply to this comment and I can detail reasons why, most likely in a full fledged post.
(Over the next 3-5 years, I believe "market returns" - defined as those received from SPY ETF - are likely to be less than 6% from this point (Dec 23 2016), possibly significantly so.)