Hi Jonny
A bit pressed for time but will throw a couple of thoughts in the pot for further discussion
To me, it depends on what art you are training in traditionallY and what you want to get out of your art.
If we're talking about just the physical aspect of self protection, then of course, there may be some arts who's base techniques are better or worse suited to a self protection situation in the street.
However, if you are focusing more on the mind set aspect of protecting yourself then training the traditional way in a traditional art can be a very good solution if you ask me.
Some of my toughest training sessions, the ones that shaped me the most as a budding martial artist and perhaps the ones that have given me the grit and determination to drag myself through tough tough fights outside - have come from my "traditional" karate days training with Geoff and the other guys in our early Shotokan Karate club
(phew - long sentence - sorry)
The attitude to your training can be seen to be far more relevant than perhaps the techniques and I feel the way traditional arts such as Karate, Judo, approach their training are great for developing this attitude.
You could argue that walking up and down the dojo throwing punches in the air, or sat in a Keba-dachie (spelling mistakes - sorry) throwing straight punches is not very realistic. But let me tell you, if you can do that to the point of failure in the dojo - that strength of will is the thing you are going to be calling on when you've got 20stones of muscle bound goliath trying to make you eat tarmac and you'e got a choice to cover up and go down or grit your teeth and find some resolve to carry on. Technique is out of the window then - attitude, mindset and strength of will is what will pull you through.
Trad arts have that in stacks - providing it's trained correctly
On the flip side - some RBSD (and whatever other acronyms we can come up with) classes, have all the so called "realistic" techniques but still miss the point when it comes to the real area of self defence - the defence against "the self"
Self Protection starts with the "Self" (I'm using that on a t-shirt so hands off everyone)
If your training doesn't cover this then doesn't matter what you train in - if you ask me
Sorry - longer response than I thought
Take care
Al