Still running MT4 for most of my EAs because my brokers push it and my old code just works. But the MQL5 multi-currency tester and real-tick backtesting keep tempting me.
Who has fully switched and never looked back? And who tried and went back — why?
Switched in 2023, never looked back. The multi-symbol tester alone justified it — I can finally backtest portfolio-level EAs honestly. Porting was 80% find-and-replace and 20% swearing at OrderSend semantics.
One caution: my broker's MT4 spreads are still tighter than their MT5 on some pairs, for whatever reason. Check execution costs per platform before moving — a 0.3 pip difference can evaporate a strategy's entire profit.
MT4's only real moat left is legacy custom indicators that were never ported. If you're not chained to one of those, switch. If you are, port it or pay someone to — the tester pays for it within a month.
I am chained to exactly one legacy indicator. Story of my life. Porting it next month, then MT5 for good.