Although I generally hate vs. threads, there are some valid points made here. I look at it from the perspective of this, all styles bring something to the table of value, and while I certainly would not call them equal, they all have something to contribute to overall spectrum.
Kung Fu- Many styles but from what you are defining more of the Northern style, high kicks, angle kicks such as crescents, hooks, ax, ect can be hard to defend if you are not familiar with them. Also, donkey kicks and stop kicks can be greatly effective.
Karate-Again not all Karate is inclusive, but most Karate is trained with the intent of using angles and strong, fast strikes to disable quickly. This is not always the end result, but Karate, such as Kyukoshin, can be trained and used effectively. (Training Methods!!)
Boxing-Simple yet effective, no other MA'st punch like boxers, because it is what their entire style is built on and all they train. Entering and exiting strategy is very good, however, due to their method of bob and weave and the amount of weight they put on the front foot of their stance sets them up to get ate alive with leg kicks and knees (as well as not knowing how to defend kicks of any kind).
Muay Thai- Been said over and over again, strong clinch, strong knees and elbows, strong power kicks. Mostly ****ty hands. Still one of the better styles IMO.
So how do you get the best of all? You train and spar from all of the above, if you train it and know how to do it, you also know how to defend it. It is also of great importance to look at training methods to improve your existing skill set. Boxing and Muay Thai added weapons to my skill set and made my existing Kung Fu better. Now if you want to argue about what it is you actually do, I don't care about any of that garbage. As I said, all styles have worth to them, some much more than others but you can learn from all styles, as well you should.
Drinking from the same well over and over does nothing but become stagnant.
"The hero and the coward both feel the same thing, but the hero projects his fear onto his opponent while the coward runs. 'Fear'. It's the same thing, but it's what you do with it that matters". -Cus D'Amato