FreestyleJJ - Huge difference when playing guard. Its much harder to setup a subtle slow setup while worrying about being punched.
Also the guy in top may try to just stall and press in a lot. Another bjj guy will open up more and try to pass.
That being said the level of bjj in mma IS really poor. A lot of A class athletes get away with it for a long time because its hard to make them pay for it. So then they make it big and play catch up. By that point its hard to convince them what they've been doing is wrong.
I see a lot of low level mma fighters with atrocious bjj and they get crushed. So bad that i have to wonder why they even bother getting in the cage without even the basics down.
If the level of grappling in MMA is so poor, why doesn't Maia submit his opponents more often? Why don't the countless blackbelts who get into the UFC do better, instead of getting bounced after a couple of losses?
Would it be easier without rounds? Yes. But it's not like we're seeing all these blackbelts almost have something and then be cut short by the end of the round. More often we're seeing them smashed on the bottom, unable to get any offense going.
Everyone has decent grappling now, especially sub defense. Not the easiest thing to work your game against a strong, sweaty guy with an endless gas tank who is punching you whenever you let up.