Gr2 only has reflectivity, velocity, and spectrum width. I only use the reflectivity and velocity. GR3 has those two but also storm tracks, precipitation, TVS, meso, hail. comp ref and a few others.
The difference being L2 data has much better resolution. Your seeing the same data but more enhanced. The dbz scale on GR3 goes 5-10-15 etc. GR2 goes 2-4-6-8 etc, so that same data is broken down even further. It's easier to see rotation in velocity mode and hook echos in reflectivity. It also has a neat Cross Section option where you can look at the storm in 3D from any angle or elevation you want.
Plus the range goes out much further which was a big selling point for me.
As for Analyst, yeah it's pretty expensive but man would it be fun to play with. Being able to break down storms with a true 3D image would be awesome.
Your are also right that Analyst data is much more data and CPU intensive but I'v upgraded my machine so it can handle whatever I throw at it.
Also since I purchased GR2 that price comes off the top of Analyst.
Now I just have to convince the wife that I really do need a 3rd radar program.
That will take some doing.