If they ain't broke, don't fix 'em. A friend of mine got the locker with the side gears and had trouble with them staying together. He traded for the one without and has had no trouble since. I've had my locker without for over a year with absolutely no problems. HTH.
Side couplers are a waste of money. We don't even sell them since they're such a waste. Retailers that do are just looking to make a couple extra bucks. Ask around to those who have run the side couplers and half the time you'll find more problems associated with getting them than problems solved. If you need new side gears, just get factory replacements.
The first locker I bought and installed in the rear had side gears. My second set for the front did not. The rear pops and bangs alot more than the front. I have replace the springs in my rear locker hoping that would improve the action. I am thinking of going through the trouble of moving the front locker to the rear since it is use more. To sum it up do not spent the extra money.