I have made the switch and I doubt I will ever buy another W123 unless I stumble across a rust free turbo wagon. The W124 is light years ahead of the W123 in terms of everyday drivability. I haven't needed to do any major work to either of mine yet so my opinion of them may change. FWIW both of my cars are M103 powered but the gas mileage isn't great. I get about 25 in the 5 speed and 20 in the autotragic. I prefer to drive them over my wife's 2014 CR-V.