note: this is only my opinion it may be right but most likely im just full of it

I dont like the co-pilot to train on. I see it as a crutch that can start to be leaned on too heavily too quickly. if you get used to letting go of the sticks when you get in trouble how are you going to learn how to recover from a bad situation.

I learned the hard way. I got my "pilot" rating at my local field and one day while practicing stalls and such I got into a spin. so i corrected and pulled up... right into another stall spin, repeat until about 5' from the ground. this is the EXACT moment that I realized that no matter what situation you are in a cool head and smooth thumbs can get you out of most anything. I saved the plane with about 6"-1' to spare. (from the "peanut gallery" I heard someone yell "Stick save!!!!")

if I had a co pilot I might not have learn that lesson.

I am a firm beliver in the school of hard knocks.

you **** up, you learn not to do that again.
(I learned to ski that way ... fall "ok thats not a good idea", fall again "neither is that" soon by prosses of elimination i found out what worked )

now I do belive in a instructor because he can let you try to recover the plane and then grab it from you if he thinks its too close... meanwhile you shouldnt stop trying to recover it until after the instructor grabs control. this way you can learn to recover from stuff without letting go.

I can see letting go become a trained reaction to a bad situation with the co-pilot, you might not think it but some day you might get into trouble and you will let go without thinking expecting it to recover.

but that is just my opinion and like I said there is a good chance that anything I say could be worthless