afaik the gripper diff is good but the weak point is the crown wheel & pinion & when it breaks it could take out the lot so very expensive .but the supra diff is pretty much bomb proof & the turbo versions were lsd as standard .And are a bolt in conversion no welding needed at all .you can pick up second hand diffs for £125 delivered as well
http://www.tcbparts.co.uk/ ask for Trevor.