To me I'd determine linear or harmonic by what's there already. Like dirt said, it's so much easier replacing like for like. I'm not familiar with the MAC operators, but if they are harmonic I'd look at seeing if a GAL Movfr2 can fit in easily. It would be a perfect complement to the controller your using if it fits mechanically. In my opinion most of the operators now days are so reliable that there's really no drawback to an operator like the MOVFR and being able to split the doors is a huge benefit for service/maintenance. My biggest jobs are a couple 10 story hospitals with 7 to 15 elevators in each one. Over 20 of the cars have been replaced (including new cabs) in the last 5-10 years and could have been spec'd to anything. They could have bought new cabs with linear operators. Every single one of those 20+ cars have a MOVFR on it and gets hundreds of trips/door cycles every day. I almost never have a callback for anything related to the operator.