You must remember, that in self-defense, the objective is TO ESCAPE. This has been stressed by many with real life street experience, such as Marc MacYoung and Geoff Thompson.
That being said, you cannot run away while engaged in grappling on the ground. Geoff Thompson, as a bouncer, re-counted an incident in his bar where two fellows were grappling on the ground, and one of them got knifed repeatedly by on-lookers. Marc MacYoung has re-counted several instances where two guys were grappling on the ground, and one got stomped by onlookers. Neither believe in grappling as a first-response, as it is does not account for multiple opponents (often a reality!), does not allow quick escape, and can be dangerous if the assailant is armed (which you may not know at first glance!)
I believe that some essential ground skills, if you happen to get taken down (such as escaping from mount, quickly getting to your feet, etc) are VERY important. Otherwise, how will you react if you do get knocked down and someone's on top of you smashing your face in?
HOWEVER, because the objective of self defense is to escape, a strike-based offense, followed by quickly sprinting away from harm, is much more safe than going in for a takedown and grappling on the street with someone. Grappling prevents immediate escape, opens you up to friends of the assailant, and puts you in a very dangerous situation if the assailant has a knife (you don't grapple with bladed weapons, this a very bad idea).
Running away (sprinting away!) should always be the prime objective, the goal of self defense is safety. Strikes allow for this more than grappling does, though I still believe some grappling training is important, in the event if you get taken down.
Never confuse the ring with the street, they are very different. Ask soldiers or law enforcement questions like this, they are the ones who regularly deal with these realities (martial artists tend to hypothesize about a lot of things that have no real experience with) - this can be very dangerous!
P.S. From the training options you mentioned, I'd say kickboxing would be a great bet, along with some practical groundwork as I described. You also want a training program that practices against resisting opponents (not just punching and kicking in the air or against a static opponent) - because that will condition you correctly for a real conflict, which will surely involve a resisting opponent!