I can 100% report the same thing - the closedsource xptminer2 on Riepool reports better hashrates than the opensource xptminer on ublock. But I did about 2 weeks on Riepool before growing frustrated that my own miners were solving blocks at a much higher rate than that at which I was getting rewarded. The difference was significant, too - not just a function of the margin of error. On ublock, even though the opensource miner reports much lower hashrates, I'm actually earning a great deal more, and my miners are getting rewarded appropriately for the number of blocks they solve. This leads me to believe that either the closedsource miner's hashrates are being artificially inflated or Riepool is suffering from too many block-withholding attacks.