Harder on engines, EWS or Flemington?  

EWS for sure. As others have said Flemington was a momentum track. Fast story, in 1978 we won the TRi Track race at Flemington with Billy O driving. Something happened to the motor at about lap 50. I don't remember what was wrong but that baby was sick. Trust me the pace car had more horse power then 73 for those final laps. Didn't matter still won by nice margin. To take it farther (because the actual question was which track is harder) a motor that runs on consistant RPM's is happier then one that has to shut down in the corners and reach peak at the end of straghts twice a lap.