As for the anti-rock, whether you're better off with or without one depends on what you do with your rig and how you're setup. If you mostly pre-run, I can really see it. If you're setup relatively soft for mostly trail work, it could also be an advantage. Some of us are set up relatively firm for great trail stability and hauling ass to and from the trail, and while we maybe would get a benefit from it while hauling ass it's not necessary on the trail. I've had setups where it would have been good, but the way I am now I don't want one. Most trail guys use it to add stability, if they need it. If you already have good stability, it's just no benefit.
Many comp rigs and rock crawlers run soft slinky suspensions that lack great stability, so they tend to lean on sidehills and off camber situations. The anti-rock type sway bars help this situation. Especially on a comp rig stability is important because of all the crazy positions they get into. However, if you look at most of the moon buggy type rigs, which have gravitated towards running 3 links front and rear, they use very high track bar placement to create a very high roll center which provides enough stability and most don't run sway bars.
Another thing is the shock setup. Many guys have started out running coils, which are slinkyer than leafs and many times require a sway bar, then they went to coilovers without tenders which pushed up too much on the uphill side making them unstable so they used sway bars, then guys started running air shocks which are inherently less stable and can push up more than coilovers so they really needed sway bars. Now guys are learning to run tenders on the coilovers and better tuning on the valving and springs, setup to also go faster because of the rock racing, and they've learned much more about setting up their air shocks. There are also more rigs built with high roll centers and a lot more three links.
My buggy has VERY high track bars and roll centers and I've had a number of people who know what they're doing comment on how incredibly stable it is. Well, I built it to be that way (luckily it worked
) and it has no use for a sway bar.