Communication is the unseen edge in paintball. It's one of the most important aspects of woodsball and even paintball as a whole. Without communication, your potential 1^st place team is turned into a pack of unorganized barbarians that any competent team can take out.  In woodsball, communication is even more important; avoiding ambushes and knowing which part of the field is laden with explosives will definitely keep you playing longer.

Players who need communication the most are the lone wolves.  If you’re a sniper with multiple opponents moving on your position, what can you do?  Without a decent communication system, you might as well get ready for a last stand.  However with a radio, you might have a chance of survival and get back into the game. If you're playing a back man position, using a radio to call players as backup or report to them the opponent's movement will give your a team serious edge.  

Communication efficiency varies widely. From yelling to having military grade mikes, what matters the most is how efficient you are with it. Yelling can actually be useful in firefights, but is often counter intuitive in any other situation as it will surely give away your position.  Most high end communication systems can cost a bundle, however they are the most useful and fast.  I prefer a SOCOM throat mike for my favorite type of woodsball play.  Overall, if you want to win, communication is a must.