IMHO sims are a good tool to teach muscle memory..and aerobatics....every student I've taught that had a sim learned quicker...doesn't mean you can't learn without a sim, you can...most of what you learn flying RC is how much throw equals how much aircraft reaction....and teaching your eye what you are really seeing...
the downside to sims is it can't scare the quake in your knees...and they just can't give you your full visual range....
if its a choice between flying and a sim...get flying