Quick follow up with some different EMA combinations - One was used at one point in time and here I am going to re-visit 10/50 crossover.
Period I (01. July 2008. to 01. April 2009.): 15460pts, 134 trades, Avg.W/Avg.L = 2.99;
Period II (01. April 2009. to 01. January 2010.): 2498pts, 139 trades, Avg.W/Avg.L = 2.39.
If we take brokerage and slippage into the account for first period, we could say that 10/50 was better option to trade than 7/21, as point difference is 735 in favor of 7/21 with 82 trades more, which means that with 2 points brokerage and 7 points slippage per trade that advantage is gone.
Real difference comes in period from 01. April 2009. to 01.January 2010. when faster moving averages made 7250 points. Simply, if we take brokerage and slippage into consideration, system would probably lose money during this period.
It is obvious that shorter (faster) moving averages were performing better in changed conditions, like we had during last 9 months.
Trade with trend!