A rotary switch with a pile of resistors is technically a 2-terminal "variable resistor" which is not the same as a 3-terminal "potentiometer". Leo may only need the functionality of a "variable resistor" but sometimes words matter. 
Anyway, make-before-break or break-before-make may not work because there's a discontinuity in resistance when changing positions. In one case the resistance briefly goes to infinity, in the other case two adjacent values are albeit briefly shorted so the resistance at the terminals momentarily drops. Again, it depends on the application but one can imagine situations where even a brief jump in resistance can be a deal-breaker when you expect only incremental no-hiccup changes as you increase or decrease the value.
