They are not directly competing Bitcoin in terms of blockchain technology path they are going maybe in the marketcap they are really a competitor of Bitcoin but this topic is not even related to Bitcoin so don't do off topic post.

BNB is user friendly due to its cheap fee and fast transaction. The only disadvantage I can see on BSC was it is too centralized which CZ can do what he wants on it's own blockchain so the fate of the project is at the hands of CZ while ETH is the most decentralised and safe blockchain aside from Bitcoin. The answer on this thread depends on user perspective.