I agree that Alexandra was the best but Joe probably had the steepest learning curve and was a worthy winner.
Pedant's Corner
I realise that you are merely following conventional usage, but a "steep learning curve" actually indicates rapid, easy, learning.
The term was first used by psychologists in the late years of the 19th century to indicate the relationship between a change in behaviour due to experience - learning (y-axis) and the amount of experience (x-axis). Experience is positively correlated with time. Difficult tasks take a long time to learn.
Hence, the amount of experience required by Joe would require considerable practice, effort and time to acquire - hence a lot of learning required to reach the demonstrated proficiency. This produces a shallow rather than steep learning curve.
End of pedantic interruption.