No one knife is the best, sorry. Your desire to win, cool head, good physical condition, fast reaction, fighting skills and a decent deal of good luck are essential in real life knife fight and you can't replace them with the knife. Believe me or not but this is the least important thing what knife you will have in your hand in situation when knife fight is unavoidable. My best advise for such occasions - run away from knife fight as fast as you can! and don't rely on your advantages, especially on knife as itself.
Well, just to do not leave you without advise you are looking for...
Take a careful look onto CRKT - Pat Crawford - Bob Kasper Pro folder. It is specially designed as folding fighter and will work in self-defense situation as good as knife as itself could. And it is equally useful for peaceful utility tasks. I would stick with plain edged one. However no one coin has a single side - it is a bit into bulky and heavy side for every day carry, for me at least.
Beware of Emersons, they all have single sided sharpening on the side improper for right handed user. If you are intending to use your knife for some utility tasks and not only for destroying - I do not believe you will be happy and comfortable with single sided sharpening...
Oppsss! Just edited to add - BM 942 Osborne is cool knife, I like my green 940 a lot but no way I can consider this knife as really good choice for self defense purposes.