Dusty Rhodes wins this matchup in just about every aspect you can look at.
Impact on the industry:
Dusty Rhodes: Dusty Rhodes was one of the biggest stars in the 1970's and 1980's era of pro wrestling. He put the Florida territory on the map. His character resonated with many fans and inspired countless wrestlers both on the mic and in the ring. He was also one of the main bookers for the NWA/WCW in the 1980's and early 1990's. He even has a particular finish for a match named after him. Now that is influential. When you have stuff named after you, you're important. He also gave the world Dustin and Cody Rhodes. He's the current main trainer for Florida Championship Wrestling, so no doubt he is having an impact on many of the future stars of wrestling. When you ask everyday people who aren't wrestling fans about wrestlers of the 1970's and 1980's, Dusty Rhodes is a name that comes up (at least in my personal experience). While he wasn't at the level of being a pop culture icon like Hulk Hogan, Stone Cold, and the Rock, he was up there in that era.
Kevin Nash: This is probably his strongest point because Kevin Nash did help change the nature of wrestling in the mid-to-late '90s. As part of the Clique, he helped change the WWF from going in a cartoonish style storyline-wise to the more edgy, realistic approach. He was one of the first guys who would sometimes make shoot comments in his promos. He did this a bunch in WCW especially, but even in WWE he would do this as Diesel. And his last run in the WWF before he left for WCW (late 95-early 96) is one of the earliest instances I can think of of a tweener character in the WWF. Before he flat out turned at Shawn Michaels right before Wrestlemania 12, he was on the border of being a bad guy and good guy. He wasn't really either at that point. I think Kevin Nash was pretty important on wrestling in the late '90s. But his impact on the industry as a whole isn't as big as Dusty Rhodes.
Workrate/In-ring performing:
Dusty Rhodes has this one as well. Has Kevin Nash ever wrestled a 60 minute match? No way. His longest match is maybe 20-25 minutes if that? How about Dusty Rhodes? He wrestled plenty of them against Ric Flair, Harley Race, etc. People think Rhodes was a horrible athlete because of how he looked. Not true at all. Ask Race and Flair and Terry Funk, they'll tell you Dusty could go in the ring. Appearances were definitely deceiving when it came to Dusty. Dusty was 10 times the athlete that Kevin Nash was. And if you compare great/classic matches, Kevin Nash has a handful (and I'll bet you 5 bucks that 95% of those matches were against either Shawn Michaels or Bret Hart). Dusty Rhodes on the other hand has many classic matches. Dusty was made NWA champion on three occassions for crying out loud. In that time, if you weren't a good wrestler, you weren't made champion.
Mic Skills:
Kevin Nash is actually quite entertaining on the mic. He's very good on the mic I would say. But it's always easy to be entertaining when you're inserting shoot comments into your promos. Anybody can be entertaining that way. Dusty didn't need to trash people for real to make good entertaining promos. Dusty was just a gifted talker. Up until the 1980's, he may have been the best talker in the history of the business. He was that good. Hell even with all of the great promo guys that emerged in the 1980's and beyond, there's still people that consider Dusty to be the best mic guy in history. Dusty was great.
Drawing ability:
This one isn't even close. Kevin Nash's one big run at the top of a company (the WWF) was one of the worst runs of a champion in that company's history. When he became champion in WCW, WCW went further down in the ratings and never recovered. Now I don't think Nash being champion was the reason WCW declined obviously not. But if Nash was a great draw, he could've maybe gotten some viewers back for WCW. He didn't. Nash was a poor drawing champion in both WCW and the WWF. Dusty Rhodes on the other hand sold out arenas, drew huge crowds, and was made world champion 3 times because of how popular and how good a draw he was. He pretty much made the Florida territory one of the most successful territories in the territory era (the Funks and Briscos and Eddie Graham also of course helped too). Wherever Dusty went he was popular and drew serious money and crowds. Dusty wins this argument easily.
Kayfabe Match:
I think Dusty Rhodes would win this one as well. Dusty beat legends like Harley Race, Ric Flair, Terry Funk, etc. Diesel was a big guy, but Dusty was very resiliant and could take shitloads of punishment and still win. Dusty could also easily outlast Nash. At the 25 minute mark when Nash is about ready to collapse, Dusty would fire up and easily take him. Nash was a big, strong, intimidating wrestler. But Dusty wouldn't be intimidated. If he could withstand beatings from the Four Horsemen (five guys), then he could easily contend with Kevin Nash on his own. He's "the American Dream baby!" And he would win too.
Dusty Rhodes is the right choice here folks. No matter what aspect you choose to pick your winner on. Unless you're more of a Kevin Nash fan of course.