You will get the best response in the Oneworld Forum.

The answer depends on the class of service. Is it economy (M), business (D) or first (A). With economy, you definitely have to look carefully. With D and A fare basis you should generally be OK.

BA EC is not very good for M. For D and A, you should be OK with EC but what is your status? Is it basic tier or elite tier (bonus considerations then make a difference).