All else being equal, e.g. about the same length of time training, about the same health and age, etc. AND assuming that the environment is neutral, I'd go with the BJJ fighter. He is far more likely to succeed in taking the fight to the ground (where the TKD fighter has no chance), than the TKD fighter has of scoring a one-hit knockout (which he's going to need to avoid the takedown).
That said, in a real (i.e. NOT in a ring) fight, it's often the guy who has the awareness to use the nearest solid object to beat his opponent senseless who wins--regardless of style.