As for controllers:
>Resistance type: I've had exactly three complete unrepairable failures due to physical damage in nearly 100 machines. Several that were worn were repaired, one that had a broken shell and many broken carbon disks was repaired and now works properly. Some simply needed cleaning. They are pretty much bullet proof in design, but they do at times get warm. Especially when you sew slow.
>Electronic type: I've had good results with those in use. Includes a couple factory Singer units, a Bernina 930 unit and one from Sew-Classic. So far no failures. Keep 'em dry and don't bang them around and they should last.
Joe