In Forex MT4 and MT5 are very popular. Almost all trader like to trade MT4 and MT5.
Among them MT4 is more useable. No one trader can not say that MT4 is boring.
MT4 is easy that very good for all new trader.
MT5 is editable so many expert trader can apply robot and edit some indicator and attached other indicator program.
MT5 is some update trader. Both good. Among them MT4 popular.