.NET JIT difference while using Factory Pattern and If-else or switch

I was just wandering, if I was to have a one method that handles 100 different cases based upon an enum let's say (assuming each case has on average 5 lines of code), would that actually impact performance ? How about instead of having all the code in one method, the Factory or Strategy pattern would to be used ?

The JIT only compiles the code which is actually needed at that point. So I guess it will compile the hole method of 100 cases right? It wouldn't actually know what part of that method is needed correct ? but if I was to split that method it will actually compile what it is needed right?. For example having an actions drop-down (list of 100 Car Brands)

How would that compare to each other in terms of performance?

Thanks.