The only real disadvantage of open-palm strikes is that they limit your range by a 2-3 inches, depending on your hand size. They have the potential to inflict just as much damage to one's opponent, provided one uses the proper strike to the proper target (see my earlier comments about the soft tissue triangles here
http://jkdunlimited.com/forums/index.php?topic=907.0).
I give my students the option to strike with either closed fists or open palms during sparring. The choice is based on the following conditions:
(1)
Bone Structure: I'm 6'3" tall and only weigh 172 lbs, which means I have the bone structure of an emaciated bird. If I hit a skull with a closed fist, my hand will almost certainly shatter (I'm speaking from experience, having cracked a knuckle when I was a teenager by punching a guy in the head). Some guys have hands like country hams and can punch whatever they like, so I encourage them to use closed fists. I use palm heel strikes to the soft-tissue triangle for straight punches and palm slaps to the ear/jaw/temple triangle for hooks. However, when punching to the body, I use a closed fist.
(2)
Training Goals: If you plan to compete in MMA, boxing, or kickboxing, you should always train with a closed fist since that is how you will perform in competition. This way, you are not confusing your muscle-memory with two skill sets. Closed fist strikes certainly work on the street; they just carry with them a higher risk of hand injury. If you never plan on competing, I'd say go with the open palm strikes.
(3)
Weapons: If you carry a weapon for self-defense, you need to make sure that you don't break your weapon-bearing hand so that you cannot transition to that weapon in a time of need. Shattering your trigger-finger knuckle on a guy's forehead will come back to haunt you if he pulls a knife and you are unable to utilize your firearm.
