Thinking about it further, if the orbs lacked bonuses, and especially if they actually gave penalties, players would probably just ignore/avoid them until they felt like they could capture all 5 in a single round. This would most likely negatively impact game play.
Not only this, but if they did indeed give reduced channeling instead of additional channeling, it would probably greatly extend the amount of time it took to play the game. The catch-up factor would becoming increasingly ridiculous the closer one player got to winning. I'm pretty sure this would make the game MUCH longer to complete. Unless of course, you managed to set it up to where you could get 5 in one round, which is very unlikely/hard to do.
I think the way it is currently designed is probably the best way to do it. The increased channeling is just an incentive to go after the orbs instead of sitting back and turtling. If a few turns after the beginning of the game, your opponent has control of 4 orbs and you don't have any, well, that's probably your own fault for not being aggressive enough. And at that point, you probably would be in a bad situation anyway because they likely have better board control than you do. Each mage is just as close to orbs as the other mage is in the beginning, so as long as you are playing smart and not turtling in your corner, you have an equal opportunity to grab the orbs.
