This year I made it a 'rule' that we start all ne waza bouts with one seated and one kneeling. As said above, it cuts out wasted time with both on knees trying to unbalance. It also means one focuses on guard work and the other on guard passes.
As a ju-jitsuka, the seated guard fits nicely in our ground system. If knocked to the ground, we take up a foetal guard - on our side, front side facing uke, covering with top forearm and top shin, and kicking with top foot. When we can we pop up to a seated position supported by hands behind, heels together, toes out and off the ground, spinning on our bum and stomping with either foot. When we get space we pop out to a kneeling or standing guard. However, the seated guard allows us to attack forward on the ground from the spinning seated guard, should we wish to engage. Wrist and elbow controls seem to take care of most strikes coming our way but it is a bit vulnerable to some kick attacks. These can often be avoided by falling back to the foetal guard and building back up to seated. Our main goal in self defence, though, is to get off the ground.
Getting back to that wizard, Marcelo Garcia, I love how he is always going for position first, usually trying to control uke's upper body. That fits well with the clinching style of fighting that we do. I also like that, with seated guard, the top half is also doing pretty much what we'd do on our feet. Many of the sweeps and reversals are similar to standing, too: kneel prop = hiza guruma / uki waza / yoko otoshi; single elevation = sumi gaeshi / yoko tomoe; hip push from x-guard = kata ashi dori. Gotta love principles-based fighting.