I have done 500hr inspections on both makes. I have hung around old-timers who plied their trade with magneto rebuilds. Based on the internal component quality alone I would take Bendix any day to Slicks. I would get ahold of Aeroinstock and price a set of Air Boss CMI'S with harnesses (modern Bendix are made by Continental Motors Inc, CMI). The newer designed CMI's are smaller and more compact to boot.
Or if you're feeling frisky you might consider P-Mags. The wave of the future with vacuum advance etc....
If your Slicks are new there should be a fairly strong demand on the secondary market. Type certified crowd look for these on a regular basis.
Jim