1 on 1 --- grappler
1 on more than 1 --- MT
Is this about an experience grappler vs. an experienced striker? If that's the case, I'd say it both depends on the type of grappler (wrestler will be more effective than BJJ guy b/c they're better at takedowns which bring the fight into the grappler's world)
Look, everybody has some rudimentary striking ability and some rudimentary grappling. So, all things being equal, I'd say your average wrestler can get the takedown before getting KO'd by your average joe. By the same token, a striker can still get taken down or KO'd by an avg. joe, but the chances are less. Still, because MT is effective BOTH in 1 on 1 fights AND in ... "brawls" ... I'd study MT if I was spending my nights walking around on the streets starting fights like a d-bag.
If you're talking about an experienced MT fighter with a solid clinch game and good TD defense vs. an experienced grappler with good TDs... I mean, you've got a toss-up IMHO. However, look at the current champs.. they're exceptional wrestlers or have exceptional TD defense (part of wrestling). GSP is a freak in all respects, but would you call Brock an excellent striker? What about the Matt Hughes days? Anderson and BJ don't take people down, but the TD defense is what enables them to strike and few pure MT guys are practicing TD defense like a MMA guy would. If striking won out, Ernesto would have been wearing a UFC HW belt about 5 years ago.