I've given up on trying to get the GG4 on the left to keep up with the plant on the right. I can see it ain't going to happen. The one on the right grew so fast over the past week that it got a little light burn on the top most leaves. It grew somewhere around 6"-8". I see in the flowering stage you might want to keep your tape measure handy! The little Bubba is coming along nicely. I love that strain! So strong and solid.
I'm not sure what the trait is called, but the GG4 kind of tops it's self. The main top kind of moves to the side to allow the nodes below to grow into tops. The Bubba Kush had to be topped to get it to branch out. Not so much with the GG4. I think I'll try the SCROG method with the GG4 next time. It should be a great strain for it!