I have both Classic and G2. Here are 2 more cents (MHO):

When starting out, an hour on the SIM equals a day at the field.
Once your reflexes are automatic (pushing the right stick the right direction with any orientation of the plane), the benefits diminish until you really fly, which puts the SIM into perspective.

On the SIM, I would suggest adding at least a 90 degree wind variation unless you live somewhere that has a constant, single-direction breeze.

Using RealFlight with the (automatic) zoom option does not teach a very important "real" flying skill, which is the need to keep the plane close enough to see. As previously mentioned, G2 has an option to "Look at Ground" that keeps the ground always in view, and stops the zoom feature. This option most closely simulates flying, and shows how quickly a plane can get too far away to determine orientation.

Along those same lines, G2 allows you to vary lighting conditions, which can be another lesson in visibility.

Some things are much easier on RF than in reality, like taking off, and some things are easier in reality than on RF - quite a few seasoned pilots in my club can't land anything on RF.

Here's a little story:
A new club member used RF G2 for an hour prior to his first day at the field a week ago. He flew fine, and did a couple of takeoffs. The plane he had was used and was previously set up. He then used RF for a few more hours last week. On Sunday, he was at the field with his plane, in which he had installed a new radio. I noticed his control surfaces were waaay off center. After speaking with him, he and I went over the entire plane and made everything right. Flight one, he took off, did a few passes, I landed. Flight two, he landed himself.

Moral of the story? There are things a SIM is great for. There are things a SIM cannot do. Learn stick movements with the SIM, then go to the field and learn a bunch more. G2 is way cooler. I love it and I'm glad I bought it, but I don't know that it's necessary.