ACH is quick and effective and safe. I do it all the time between my various business, personal and my biz partner's accounts. Unless you have a timeframe on needing the money at the new bank this is the most cost effective and easiest way.

a wire will cost money - take 24-36 hours depending on the time and day of the week.

You can also request a bank check from Discover (assuming you have a physical bank to go to) and deposit in in Ally.