One of the biggest debates in the BJJ world will probably never have a definitive answer. Advocates of the gi, but train both with it and without it, usually say that training in a gi will improve your nogi. There are several reasons for this; firstly, the gi offers friction between opponents that doesn’t exist in nogi. You can’t just depend on sweat to slip out of escapes. You have to know the exact technical escape for the situation you are in. Secondly, gi offers many more techniques that can be done utilizing the lapels, sleeves and other parts of the kimono. They argue that not only does this make gi more fun and thought provoking but it prepares you to be more aware of your opponent’s attacks, therefore making it easier to be ready for the attacks in nogi.
Guys who equally train in gi and nogi, will usually argue that they are both so different that each side of the jiu-jitsu game has its benefits and that you should just practice both like they do. The physical benefits of nogi are that the pace is much quicker because there is less to grab on to and you have nothing absorbing the sweat. In gi, it’s much easier to control the pace of the match because you can slow down your opponent if necessary by using multiple grips on the kimono. So to break it down, nogi will push your cardio more than gi, but gi will develop your muscle endurance more. If you do have the time and interest, training both is always great fun.
The perspective of many pure nogi guys is probably the most ‘religious’. You will see more gi practitioners adding nogi to their schedule than guys who train nogi adding gi training. As mentioned earlier, gi practitioners are aware of the benefits of nogi training and are more confident to add it to their game. This is because they share similar movements and they even find them easier to do. They don’t have the threat of attacks with the kimono. Pure nogi guys usually dismiss training in a gi altogether for several reasons. Mainly because they feel that training with a gi is more for sport and does not offer any ‘real world’ applications. This topic in itself is a debate since gi techniques can be easily applied to clothed attackers, especially if they are wearing a jacket. The other reason, which they don’t like to admit, is that it’s just too frustrating to deal with the kimono after training so long without one. There are just way too many new techniques for them to consider that it can be overwhelming. Lastly, it can be argued that nogi jiu-jitsu requires more pressure from the top because since your opponent is slippery, it’s easier for him to move around.
The truth is that each branch of jiu-jitsu has it’s own benefits and faults. Ideally, everyone should train both and give them a proper chance. Both are useful and compliment each other, regardless of what others may think.