I vote CLEARVIEW!!!
FMS was also for me not realistic enough. Indeed Clearview can seem unstable at first, but that it is like in the real world.
For me, training with the Belt CP model in Clearview inproved my fying with the HBFP a lot. The Belt CP is not to responsive in Clearview, great trainer.
After that I moved on to the T-rex 450 in Clearview. As I was planning on building an T-rex 450 clone. In the meantime I have build, flown, crash, rebuild (Ah you get the picture) the baby. The real thing flies great!
I can honestly say, I've learned a lot from flying Clearview.
If a model is to responsive for you , go to SETTINGS and then EASY MODEL SETUP and try some NEGATIVE EXPO (eg. -20 on Rudder, Ailerons and Elevator). Be aware that on a DX6i radio you have to use POSTIVE EXPO to make the model less responsive around mid-stick.
Alternatively you can also change TRAINING TIME SCALE SETUP, which alows you to slow down time. I didn't since I considered this cheating, can't be done in the real world, will you can change the expo settings on your transmitter.
Hope this helps,
Martijn