[SirensOfTitan]

They're likely both good starting points. From a cursory glance of Spring 2015, here's why I like 2013 more:

2013 starts with Functor and builds into Applicative then Monad. I like this a lot, as each builds on each other: fmap has a tight relationship with <$>, and Monad is pretty much Applicative with bind (>>=). Applicative is a Functor and Monad is an Applicative (as of 7.10 I think).

I'm by no means super experienced here, but the 2013 course was the first learning text that really got me into Haskell.

[ac]

> fmap has a tight relationship with <$>

Yup, it's really tight: <$> is fmap