Alterraun Verner vs Bobby McCain is a pretty good contest. For the past 2 years, Verner was paid $6M per season by Tampa Bay because he was a CB in high demand based on his performance in his rookie contract for Tennessee. In comparison, Miami has got him for just $900K with nothing guaranteed - so we have got him on a bargain basement discount. We have a stack of decent CBs with Maxwell, Xavien Howard, Tony Lippert not to mention Cordrea Tankersley, but Verner has a genuine shot against McCain in the slot.
The other side to it is that Bobby competes hard against Jarvis Landry every day and this has helped to improve him. Many on FH will dismiss McCain based on some of his struggles in past years but I genuinely think that you may be underestimating Bobby's improvement - it is real. McCain is also considered the elite trash talker on the team and the coaches apparently love his feisty competitive attitude.
I'd like to keep both of them. My prediction is that Bobby holds his spot.