It’s a basic question. Should you wear the pajamas when you wrestle or should you not?
Depends on your goals. If you’re interested in self defense, you should do both. Most of the time, attackers will be wearing clothes that you can grab on to and use for leverage. The Gi simulates this. Sometimes, attackers might be shirtless or wearing tight fitting clothes. No Gi will simulate this. Do both and you’ve covered a fairly decent range of situations.
If you want to fight MMA professionally, you should probably only do No Gi. If you want to compete in Gi tournaments only, I guess it makes sense to only train Gi. For most of us with more general goals, though, it makes sense to enjoy the variety.
Justin’s Wednesday night class is No Gi every 1st Wednesday of the month! Come and play.