Expert Advisor vs copy trading

The transparency gap

With an EA, the behaviour is fixed. You may not be able to read the compiled code, but you can observe that it does the same thing in the same conditions, and you can test it. With copy trading you have a track record and nothing else — you cannot know whether last month's results came from a process or a run.

The risk that follows is style drift. A provider whose returns fall can start increasing size to recover, and the first evidence you get is a drawdown much larger than their history suggested.

Latency and sizing

Every copier introduces a delay between master and slave, and the effect is worst on fast entries where timing matters most. A small edge can be consumed entirely by copier slippage across several hops.

Position scaling is also cruder than it looks. Scaling by balance ratio ignores your own stop distance and the broker minimum lot, so the risk you actually take can differ substantially from the source.

Prop firm restrictions apply differently

Many firms prohibit copy trading outright while permitting EAs, and several treat identical trade sequences across multiple accounts as copying regardless of intent. See can you use an EA on a prop firm account.