If you play paintball in the woods, you have probably seen a few milsim - or military simulation - markers. These paintball markers look exactly like real guns, some are even clip-fed. Although this makes the game of paintball more war-like and exciting, you may want to look into a speedball marker instead of that cool looking Tippmann MP5 replica. A speedball marker will cost just as much and will be lighter and more efficient.
A speedball marker such as an Etek 3 costs just as much as a Tippmann X7 modified to look like a realistic gun. For example, a X7 with the "Extreme Enforcer" modification from RAP4 is about $700. For that much you could buy an Etek AND a rotor! You can even go down to a lower end marker with an Invert Mini or Dangerous Power G4 over a modified Tippmann A5 or 98. Clearly, speedball marker does not cost anymore than a woodsball marker.
A speedball marker will also be much lighter than a Tippmann or BT marker. Since woodsball markers are designed to look realistic there will be extra plastic, metal, and aluminum added to gave it clips, tactical rails, scopes, etc. A speedball marker is designed to be light; many are under 2 pounds, a tippmann X7 is 4 pounds. This means you can keep your gun up at all times, ready to fire. A milsim marker will take much more effort to keep level, and the more effort you use just keeping your gun up will take away effort you could have used to run, duck and slide.
Milsim guns are generally not as air efficient as a speedball marker. You can get pods upon pods off a G6R or Etek, some milsim markers can't even last a full game with a steel HPA tank. Less time filling air means more time on the field, not to mention there are less ways for you to get out of a game other than an actual paint hit.
Overall a speedball marker will be more efficient, lighter, but just as much money as a milsim marker. Speedball markers will work awesome in speedball, and they will also work great in woodsball. On the other hand, a woodsball will work okay in woodsball and won't work well at all in speedball. If you are looking for a marker to use in woodsball, look into a speedball gun.