If you want to fly jets get an A320/ 737 type rating instead of the ATR. Since you are saying what if an A320 driver was compared with an ATR driver for an airline that operates jets...
But I'm guessing you don't have an option right now and hence your question appears strange to say the least. You should be comparing a guy with an ATR rating Vs a guy with no experience on turboprops/ jets, in which case the former would have the advantage. Some people try to get as much multi-engine time as possible as it will be an advantage when applying for an airline, never mind 2000 hours in turboprops!
If I am understanding this situation wrong, pardon my ignorance, perhaps you could shed some more light on the situation you are in. Have you got an option of an jet a/c rating Vs the ATR?