You do run the risk of fouling a spark plug by constantly choking it to shut it off....and if you do decide you have to restart it moments after choking it off, the engine can oftentimes be cantankerous to get going even if the plug isn't fouled simpy due to the excess fuel in the crankcase. Kill switches work fine, but the cheapie ones supplied with most kits can short out and cause grief....so if using a kill switch, it might be wise to buy a better one. Myself, I simply set my idle speed screw to such a low speed that the engine actually stalls when I back completely off the throttle. Yes, this means pedal starting it each time I come to a stop. But, I figured if I set it this way, I'd have no choice but to pedal it instead of being tempted to release the clutch from a standing start.....thereby reducing wear on my clutch. I removed the clutch cover from my Dax a few days ago and didn't find even a trace of clutch dust....and it now has well over 600 miles on it. I still have an operational kill switch installed just in case the throttle ever decides to stick, but I have never used it or the choke to shut down my engine.
EDIT: I should clarify that when I back off the throttle with intentions of shutting off the engine, I first pull in the clutch and lock the pin. If you don't pull the clutch in first, it will still stop...but it comes to a rather abrupt and jerky stop which can't be good for it