Depends what you're fighting for I guess; competition medals, street survival, or simply to prove that you're the roughest, toughest, meanest fighter in your dojo. From a karate perspective, if it were in a regulated environment (i.e. with rules), I wouldn't want to get anywhere near a floor fighter because we don't train to fight there. Karate is not a complete system in and of itself. For a striking art like karate to be effective against a grappler, it would require a well-aimed strike before you get taken down to the floor. As I'm getting older, this is the kind of distance I am beginning to favour:
“Remember what Gichin Funakoshi said ... Karate ni sente nashi ... there is no first attack in karate. Understand this concept, mentally as well as technically. You must do everything possible so that the opponent understands it is better for him not to attack. This is the true meaning of the saying Karate ni sente nashi, that the opponent does not begin attacking and so there is no fight.”
Taiji Kase Sensei (1929 – 2004)