Its funny how everyone has completely misunderstood the question. I believe the post asked what goes better with ECN account MT4 or MT5. To which I can suggest that it really doesn't matter whether you use MT4 or MT5 with an ECN account. If you are getting raw spreads starting from 0.0 pips both the platforms will provide you the same results. However the MT5 is quite advanced from mt4 and you get plenty of additional features like market depth, more indicators, more timeframes etc. So it completely depends upon the comfort of the trader, efficiency wise both will give you the same results.
It is all up to you. I prefer use the MT4 platform. I see more functionality there. And I'm already used to using only it. So this is up to me. If you are a beginner, then try using MT5. It's easier to use.