Choosing I trained for 4 years in Hapkido. I relocated and have been in Taekwondo for 2 years. What I want to learn from the martial arts is how to defend myself in any real life situation. I learned the basic kicks, pressure points, falling, hand and kicking defense, and point sparring. I have learned distance, decent footwork, as well as throwing multiple hand and kick combinations. I friends that are black belts in many different martial arts, and we meet once a week to teach each other what we know. I think that after 6 years in martial arts I should be much better at stand up fighting. Many of my friends that are in kickboxing are much better than I am, and they have not been training nearly as long. I am pretty good at Taekwondo sparring but when I put boxing gloves on and spar against other martial arts it is different? I think they are better because Kickboxing teaches straight punches, high and low, kicks to the thigh, punches to head, and mixing it up. They also teach more basic blocks which in my opinion work much better. In Taekwondo and Hapkido, we CANNOT kick to the legs or punch to the head when sparring. I realize this is for safety reasons and against Olympic rules, but it is not against the rules in a real fight. I realize I can still do these things in a real fight, but if we do not train it, then what? I hate this about traditional schools!! I have talked to my instructors and they say do not do this, or do this differently, in a real fight, so why are we learning it then? Am I at the wrong schools? Should I try MMA? I have learned some basic jujitsu, judo throw etc., from my friends and I like it but I like stand up fighting and I feel like I am not getting it in Taekwondo? Does it take longer? Should I stick with it? Should I cross train, such as Taekwondo for a while to work on footwork and kicks, boxing to work on punches, and Jujitsu to work on ground fighting, or should I stick with one style?
Lots of questions but I think I can answer all them in one response. In choosing any martial art, you want to find one that best serves your purpose and fits your body type and personality. As an example of what I mean by body type, if you are big and powerful, then a soft, graceful style would probably not be a good choice for you. As an example of what I mean by personality, it you are a quiet, non-aggressive person, then full-contact fighting would probably not be a good choice for you.
As to your purpose, you state that you are looking for a martial art that concentrates on self-defense. All types of Taekwondo are sports oriented, and most traditional styles of karate concentrate on the budo, the way of life of the martial arts. These arts may be used for self-defense, but that is not their primary purpose. Some people think kickboxing is good for self-defense, because it uses full-contact, but it is still a sport and uses safety rules and equipment. One could still argue that, on the street, it is better than Taekwondo, but self-defense oriented martial arts would argue that it is a poor replacement. The same arguments may be made for the mixed martial arts. All these arts train against likeminded opponents; whereas, in self-defense situations, you will most likely be defending against people who untrained in any martial art, they are just evil, mean people who will risk their own lives just to hurt you.
If you only want to be highly effective at self-defense, then you should choose a self-defense oriented martial art, such a Krav Maga. However, a problem with these types of martial arts is that you do not get the enjoyment of physical competition against other people that you get in other martial arts. If is near impossible to find a martial art that has competitive sparring and also is self-defense oriented.
Cross training is an option, but cross training causes problems when in self-defense situations where you must make instantaneous decisions and actions. When you cross train ,and are in this type of situation, your brain takes too long to access the situation and take action. For example, let us say you are a businessman who travels frequently between the United States and Great Britain, and you drive a lot in each country. Everything about driving in the two counties is about the same except you drive on different sides of the car and the road. After awhile, you will probably be able to drive effectively in both countries, but when a child suddenly runs in front of the car, how will you brain react? Will it have the correct foot press the correct pedal, or will you swerve in the correct direction?
When you spar with kick boxers using their rules, you feel awkward. If they spar with you using Taekwondo rules, they will also feel awkward. Football and flag football are played basically the same, but they are different enough that players from one will feel awkward when playing the other.
Self-defense skills are a good thing to have, but for 95% of the people, they will never be needed. Most martial art masters who have trained their whole lives in their arts have never had to use their skills on the street. If this was their only goal in their training, then all the training would have been a waste of time. However, they trained in the martial arts for other reasons that made their lives better for it. There is still a possibility you may need to defend yourself. If this occurs, you may not have the best techniques for it, but you will have techniques that are effective.
You just have to decide what it is you want to do in the martial arts and then do. You can be a subject matter expert at one thing, or be generally knowledgeable about everything but an expert at nothing. Just make decision on a martial art, an instructor, and an organization that best suits your purposes and is available to you, and go for it.