HYIP / ponzi schemes operate by paying investors returns using capital from newer investors. With masternodes, no capital changes hands, it is retained by the masternode operators at all times. All returns are paid from newly mined coins, not from money invested by newcomers. A masternode owner may cash out his coins, or his earnings, AT ANY TIME. There is no pyramid, just a small army of investors running nodes for daily earnings with no obligation to anyone other than themselves.

On XMR vs DRK, both are interesting coins. The big difference for me is that DRK is working & scalable RIGHT NOW whereas XMR is more like an experiment. The market appears to agree.

Of course, the recent DRK price action could be an EVO-related pump to clean coins, although this would in fact be a good demonstration of DRK utility.