This vid pretty much clarifies the difference between kickboxing and TKD. The kickboxer is in the red shorts, and the TKD dude(s) are in white uniform.
guess what is the most used fightstyle in PRIDE or UFC ?
its mostly muay-thai/kickboxing.
here is another example>> http://www.bagarres.com/fights/muay_thai_vs_t
aekwondo
No style is perfect, but I do Tae Kwon Do and for a black belt this guys is an embarrasement clealy scared of getting hit or trying any other combination other than the poor roundhouse. Don't judge TKD as a whole by this guy as he is nowhere near being a suitable representative. The kickboxers sparring is very good, very light on his toes but I still prefer Muay Thai...Peace