To start with, our scheme on defense results in giving us some of the same qualities of a zone. We packline all the gaps. We aggressively attack the ball out of helpside on drives to the basket. And then coming out of help we rotate to the next pass with the closest defender which results in lots of switching when we are forced to rotate into help. So in either case in requires two things, or it doesn't matter if we are M2M or zone, on-ball defender must guard his man and gap defender must stop penetration before they get deep enough to force our help side to rotate over. We had been doing both of those things really well all season. We did both of those things very poorly vs Alabama. We also gave up a few too many open shots due to poor transition defense.
As to the basic question of playing M2M or Zone or having both, in football the saying is if you use 2 QB's then you don't have a good QB. Not completely analogous but it correlates fairly well. I have always schemed my team defense based on personnel. I prefer M2M and will use it any time I have the personnel to run it. But, I had a team one season that played exclusively in an extended, pressure half court 1-3-1 defense. And we were really good at it. But to be that good at it consumed lots of practice time and just the preprogrammed habits of the players. So when you think about also playing another defensive scheme there is a cost. Practice time and player habits. Players now have to think more when you change to that other defensive scheme (2-3 zone for instance). They now play slower. And your primary defensive scheme suffers as they lose practice reps and habits suffer slightly. I am not saying you completely disregard it. But it's best used as a 'trick play' meaning you only use it situationally and very briefly. Otherwise, IMO, the cost will outweigh the benefit if you try to run both extensively.