i think gi trainning is a great complement to no gi trainning. In the end its about what you are gripping. Sure you cant use collar chokes without a gi but still there are planety of gi techniques that work by just simply changing the grip on the gi sleeve to a wrist or forearm grip. Sweeps are a great example of this. I think its much easier to sweep in a gi but i can still do it wiht out one. Submission and takedowns are the same way. best example i can give of gi to no gi conversion, Karo Pariysian's throws in the mma world. I was talking to my friend who is a brown belt in judo and he said all those throws are modified judo throws.