Birky. High initial cost, low long term cost. Paid 300 for used, fresh rebuilt unit, now going on 3rd season without failure or rebuild. Uses standard cr125 clutch plates I believe. Have also used 4disc tomar, good clutch also, but rebuilds are costly.
whatever clutch you decide on make sure it will handle a good bit of hp so if you decide to upgrade to a 125cc or bigger you won't have to buy another clutch, just trying to save you some money farther down the road...
IMHO - Tomar TD-43 or SMC axle clutch re-worked by Pudge Engineering or Horstman Big Sprint All run with j/s. Value/Dependability/all 3 appropriately tuned will handle Big HP and/or Heavy Loads w/o compromise.
We got ours from John Hilton used. Since 2009 we have put 2 sets of clutch disc, new seals and tungsten weights in it and have never had any issues with it. I would highly recommend it for the higher HP engines.