If everything is equal and both Surtain and Farley are there, I think they'll go, Farley. Fish did a piece on Quinn's Podcast interview. In it, he talked about what he was looking for in his CBs and he mentioned Richard Sherman like triads, meaning smart with excellent ball skills. I'll see if I can dig it up ....
Farley is the far risker prospect when you consider Surtain, has NFL Bloodlines, played on the #1 program in the country, has no durability concerns and is advanced beyond his years on the technical standpoint.
In my opinion, Surtain is good starting corner day 1 in this league, but this is probably the best we are going to see him. Many have compared him to Bryon Jones. He will be a shadowy, sticky corner, but won't make many plays on the football. Not worried so much about his lack of deep speed, but rather him facing a small/quick type of receiver. I know they cannot workout the players, but if they could, I would have him cover Amari Cooper, let's see him handle his quickness in and out of his breaks.
Farley is new to the position, needs some development, has durability concerns, but has that natural talent you cannot teach. He has the ability to match-up against any type of receiver, with legitimate ball skills being a former wide receiver. He has the look of a future #1 CB who can travel and match-up against the opponent's #1 receiving threat. Any time you take an high upside prospect, it's important that they have the want to be great, everything I've heard about him is he is always working on his craft, looking to get better. Might have a similar up and down season like Diggs had, but towards the end of yr 1, could be special.