Let me preface this by saying, this isn’t a discussion of which is better or a recommendation that you need to do one, the other, or both. If forced to chose between gi and no gi, chose what you enjoy more. If doing both means more mat time, more mat time is better than less mat time, don’t be afraid of the modality you haven’t done before.
Most of my tenure in jiu-jitsu has been spent in the gi. Third Heaven had MMA classes that were no gi, but jiu-jitsu was pretty much always gi when I was there. Same at Wade’s. Fight Prime is the first time I can recall having a regularly scheduled no gi class that I attended. No gi was okay, it was a thing I did to get more class time, but I don’t really remember enjoying it as much as the gi. At Foundations, with Mike, is when I think I really fell in love with no gi. Late last autumn I did gi again for the first time in years. I now have a perspective on transitioning between them in each direction.
Jiu-jitsu, fundamentally, is about angles and frames. You need to build structures to manage distance, prevent getting taken in directions you don’t want to be taken, and compound the forces you’re applying. Some folks will talk “wedges” too – I think those are valid, but they’re fundamentally still a structure you’re building to apply a force in a specific direction, so I’m going to lump them in with angles and frames. Regardless of practicing gi or no gi, you will need to build frames and make angles.
The gi allows you to reinforce frames against cloth anchors. To defend an armbar you can grab your lapel and have a tight acute angle in your elbow that will be difficult to break and they’ll have to manage to break your grip not against your own hand where the mobility of your other arm can come into play, but against your jacket where the thickness of the fabric, how tight your jacket fits, and how you’re gripping it are the big factors. These reinforcements are what allow you to slow down a larger, faster opponent in the jacket using grips. The additional hand-holds and higher friction mean even someone who’s relatively new can get a grip and have a stiff, straight arm managing distance pretty effectively between them and their partner. The increased friction and grips generally mean you need to have a solid defense too. You’re unlikely to slip out even when sweaty, so prevention is more important than response as a rule of thumb in the gi.
No gi does not tolerate frames reinforced artificially by the uniform. Rather, the natural handles of the body such as the hips, lats, and traps must be used if you’re seeking to directly control the torso. Frames must be reinforced against yourself, your partner, or the ground – features which are available regardless of if you’re wearing a jacket or not. However, this means it’s much harder to learn to control that bigger, faster partner. If you’re not creating angles with your body and reinforced frames in the direction they’re trying to go they can really make use of their physicality. Getting to a good position fast matters more in a roll because if not, you’ll likely gas yourself just keeping yourself safe. When you hear folks talk about no gi being less technical, that’s what they’re referring to; the pace is generally faster than no gi by necessity because you need to move yourself to build frames to slow your opponent down and if you or your partner are not adept at building those frames efficiently then being more physically gifted than them is worth more. You also need to be on point with your attacks. Things get slippery and folks can slip out, you need structures blocking movement in those escape directions.
That speed is the thing I struggled to most with when going from gi to no gi. I had a grip-heavy game from years of gi and judo and being so married to those artificially reinforced frames. Folks will often talk about not being sure where to grip or what to do with their hands transitioning either gi to no gi or no gi to gi, but that takes all of a couple days to figure out and it’s a pretty straightforward question to answer in most cases. The speed and having to build frames with your body though, that’s a skillset that while you can learn in gi, no gi will absolutely force you to learn unless you’re the bigger, faster guy. Learning to deal with that speed made me more technical. It’s not that no gi is inherently any more technical, you should be making frames with your body and blocking escape routes even in the gi, it’s that I could cheat and use the gi so as to not have to learn those skills until no gi forced me to. Plenty of people who learned and use those details in the gi have no trouble at all transitioning to no gi.
Going back to the gi, the thing I struggled most with was how annoying grips could be. Years of not having to actively grip fight meant I wasn’t preventing grips for a couple of weeks when I went back to the gi. I just wasn’t used to having to. I could still get my positions, my grip strength was still there when I wanted to get a dominant grip and just hold it, but getting 90% to what you want and then having to deal with a grip you didn’t prevent en route can be disheartening. You know you can do this thing, you do it all the time in no gi. And those grips allow for more efficient economy of movement sometimes. Being able to grap a sleeve at the cuff and push off of it lets you both redirect your partner and lift yourself. It’s possible, but difficult in no gi where blocking and lifting are generally the best you’ll be able to do, so there are things that are more optimized for the gi to relearn. I’d argue these things tend to be “win more” effects – effects that help you win faster or more decisively, but that rarely, if ever, change the actual outcome. You’ll have to deal with your partner’s grips, but there’s nothing about the gi that forces you to use the gi grips, your no gi game will still work and if it’s honed should still work well; it just might not work as well as if you also took advantage of the lapels and sleeves.
Gi and no gi don’t need to be that different. Grips and different chokes being available is honestly all that really changes on an inherent level, and as discussed, those are relatively minor things. The notion that either is more technical is silly – both require you to use technique to overcome physical differences and both allow for you to do so provided you’re learning the right stuff. They just require different focuses if you’re playing optimized games where you take advantage of low friction in no gi or grips in the gi. As to which beginners should do first, I think you’ll learn better defenses in the gi, but you’ll learn to not rely on artificially reinforced frames in no gi, so it’s honestly a horse apiece.
Footnote: Recognizing that you may not be hip to Northern Midwestern idioms, I’ve included a link for what “a horse apiece” means rather than using a different phrase. If you’re not from Wisconsin, you now have a new way to describe when two things are more or less the same. You’re welcome.