The final edition cannot surpass the original from 2001
Now while 1946 offers plenty more aircraft, missions and maps, the basics are still the same. The AI now seems outdated (compare Battle of Britain 2 from Shockwave, with 2.07 patch), the graphics and ground detail which was suitable for a ground pounding sim, such as the original was, isn't up to the task anymore.
In my opinion 1946 is a big (insanely big) add-on for the original title. That is why the russian front still plays best. The only other thing worth playing (other than the eastern front) are the carrier landings. There is an insanely large collection of flyable planes, but then again I would rather settle for fewer aircraft if the mission design, graphics and AI would be improved (again see Battle of Britain 2).
So in conclusion: if you have the original Il-2 get the free patches which include some new planes) and care less about the amount of aircraft that you can play, stick with the original. It is a matter of quality vs quantity. 1946 has lots of quantity, but the quality is the same as the original from 2001 (plus the original works like a charm, while the 1946 is a resource hog (the original was also, but that was 2001 and the hardware did catch up).