In order to determine which is better, there needs to be a level playing field, something that doesn't currently exist. You see, for a traditional karateka to prove his training is better, he has to beat the sport martial artists at their own game. He has to enter an open tournament, play by their rules and out-perform them. It can definitely be done, but at what cost? How much modification does he have to do to his art in order to do so? Doesn't that conformity already mean in that moment he's no longer performing traditional karate, but rather a version of it designed for sport? The reverse is true as well. For a NASKA competitor to do well at a WKF event, they have to play by their rules, and are therefore no longer performing sport karate.
This isn't a new concept, however. The entire existence of Judo can be attributed to this dilemma. Following the end of the Samurai era, where classical martial arts could be tested on the battlefield (although Japan had just come off a 250-year peace period, where it could be argued the devaluation of traditional arts as "combat-ready" had already begun), individual ryuha began competing with one another. When Kano Jigoro burst onto the scene in 1882, naturally his goal was to prove that his new art of Judo was better by implementing a new form competition. So what did he do? He invited all of the classical arts to send their best fighters in order to compete in a friendly match, that he got to pick the rules for. Not only that, he stacked the deck by enlisting Saigo Shiro, adopted son of Saigo Tanomo (instructor to Daito Ryu's Takeda Sokaku), to be his prized fighter (read more about this by clicking here). So in essence, he used classical jujutsu to prove that Judo was better than classical jujutsu in a Judo-style tournament. Yeah, that makes my head hurt too.
Let's extend that to the debate between RBSD and MMA...
The RBSD community has gotten away for too long with just sticking their nose in the air saying that what they do is "too deadly for the ring." It's become a tag-line for absolute bs. What's needed is for a practitioner of RBSD to enter to octagon and beat multiple MMA fighters at their own game. Here's where the problem starts. Again, we see the issue of conformity because yes, MMA has rules. By entering the octagon, the RBSD practitioner automatically agrees to fight by their rules or risk disqualification. If he goes in and uses illegal techniques, he'll immediately be crucified as having had to cheat in order to "win," so that's out immediately.
"On the street I would poke your eye out, bite you and kick you in the groin." Shut up. That's not the type of illegal techniques I'm referring to, because remember, if you're in a position to do any of those things, so is your opponent. An MMA fighter can eye jab, bite or groin-kick you on the street too. What I'm referring to specifically are striking targets and types of strikes. Look at the majority of self defense classes out there, and you'll see two prominent things: open-handed strikes and strikes to joints. Why? Because they work. If I palm you in the face, it's going to rock your head back and create off-balancing at the very least (if not break your nose or jaw), putting me in a better position to throw you and gain a dominant position. Now, the argument can be made that it's not that difficult to switch from an open-handed strike to a clenched fist, but just having to modify your training is conformity. The same goes for striking joints. If I thrust through your knee, your leg is going to buckle and you're not walking anymore today. Of course, I could change it to a round-kick to your outer thigh, but here we go conforming again. Modify enough of your techniques, and are you still practicing self defense, or are you now fighting MMA-style? Even if you win, did you really prove the validity of RBSD or did you only prove your ability to adapt?
In my experience, it's a mix of various training methods that each reinforce a specific aspect of an encounter. For example, this is how we train in my school, and I believe it's the combination of all of these drills that results in the efficiency of the practitioner. First and foremost, there has to be hard sparring. After all, you're only as good as the shot you can take. So we gear up and go at it (sometimes, we don't even gear up).
DISCLAIMER: What I'm about to describe below is not to be practiced without the supervision of a qualified instructor. We are not responsible for any injuries sustained through training.
In order to train more "self defense oriented" techniques, as described above, for specific drills we've adopted the concept of simulated striking. There's a difference between pulling a punch and having control. What we've done is study, through videos of real-world attacks and the study of biomechanics, what happens to the body when you strike different targets. As I said earlier, if I palm you in the face your head is going to rock back. There's going to be an anatomical reaction. So in training, if I throw a fully committed palm strike towards your face and have the control to stop it an inch from your nose where I could've hit you, the training partner will respond with the correct anatomical reaction. The same goes for if a place a full power side kick just off at an angle from your knee so I can still get a full extension. No, this method is not perfect by any means, and admittedly there is a small measure of compliance, even if only to prevent injury. But this type of training can be performed in real-time with fully committed attacks that force you to respond or risk injury yourself. And then of course, we have other drills to simulate the body's natural, biological stress response so you learn how to fight under duress... Blind-folded drills, multiple attackers, etc.
Of course, there's a lot more too it and again, my training methods are far from perfect and I'm always looking for new or better ways to impart these skills to my students. But so far, they are working and have worked for the students of mine that have been attacked. So I think to say that there's no real way to pressure test RBSD is a half-truth at best.
The biggest issue when determining the efficiency of a style or training method is context. Everything was designed to solve a particular problem, and everything works in the context it was created for. Your ability to adapt those techniques outside of the original context or not has no bearing on whether or not those techniques work. They may just not work for what you're trying to do with them. Do you judge the marksmanship of a sniper by his ability to fight with a blade? Wrist locks are often ridiculed because let's face it, as stand-alone techniques they're nearly impossible to pull off against a resisting opponent. But when you practice inserting them as the finishing move to a combination of techniques, now you've opened Pandora's box. But again, it must be practiced under duress. You must know what it's like to know that if you make one mistake, you're going to get hurt or worse. You must learn to persevere through that.
Will we ever figure out the "best" style of training? I think the answer is simply no. There's too much variation between schools of the same style, let alone across the multitude of styles out there, to make any blanket statement about the efficiency of any group. Therefore, it's not the style but rather the training methods of the individual school that will determine how effective their training is towards helping you reach your goals, whatever they may be. The only advice I can give you is to figure out exactly what your goals are, and find a school that best meets those goals. After all, nothing else matters.