Hi Alan,
Restrictions like the FIFO, leverage size.
Most of the profitable EA’s i have seen requires a larger leverage size (lower investment capital) or low leverage (higher capital). And US brokers have a maximum leverage of 1:50.
Additionally, I compared the spreads on my Oanda and Forex.com demo account. Forex.com had better spread than Oanda, however, i could not use EA on the demo. So i had to go with Oanda even though the speads were higher.
Gabe.