this is my opinion, but real stops held at the exchange are the best way to operate. For two reasons, synthetic stops rely on your price feed to know when to execute, if your connection goes down, or is intermitten, then your stop will not be executed or has a high chance for slippage. Secondly slippage, in a fast market like the ER, the split seconds it takes for your order to go from your computer to the floor could result in a tick of slippage here and there.
In over 3 years of executing trades, i have only had slippage on real stops twice that i can remember in the ES. If it ain't broke, don't fix it.