NihabaAshi, I don't think YM gets a huge amount of professional interest, apart from arbitrage programs. Apart from the arbs it's mainly small and medium sized retail traders that trade YM. Just compare the lot sizes on the YM tape (more than 100 is unusually large) to the ES tape (not unusual to see 1000 lots going through). Most professionals are trading the stocks, the GLOBEX futures or the CME pit so it makes sense, if one believes that following the professionals is important, to use the rth for equities and CME i.e. 0930 to 1600 or 1615. Of course noting the overnight action is important but interesting overnight action often begins much earlier than 0820.
Also this whole debate will soon be academic because YM is transferring to GLOBEX early next year so you may as well start getting used to it now.
