f/1.8 vs. f/1.4
Despite the 1.8 being alot cheaper in price (and also in build quality), it's widely argued as a sharper lens. I do not have the Canon 50/1.4, but I have several 50/1.4 from the same era. At 1.4 the CA is very pronounced. If you cannot live with that, think twice, or prepare to pay a bit more for the Sigma or Otus.