Ken Masters isn’t that much different from Ryu, but Capcom luckily made him different enough to stand out on his own.
If you know how to play his BFF, then you pretty much know Ken’s moves already.
Like Ryu, just because you pick Ken doesn’t mean you’re going to automatically win the match.
But Ken definitely does more damage with physical attacks than with fireballs.
So that’s why most pro players would pick Ken over Ryu.