I don't know which is better or worse, but I stay away from the house brands sold by the auto parts stores. They're generally of low quality. Though they may carry a lifetime warranty, no one wants to keep replacing clutches, even if they are free. I think most won't warrant the kits unless they're installed by a qualified garage, though.
My preference is the LUK clutch kits from Pep Boys. You can install the V6 clutch disk and pressure plate on the Duke flywheel, but you would need to purchase a separate Isuzu throwout bearing. I've been running the LUK kits for years on my GT's, and am even running one on my 3.4 swap.
I would also definitely install Rodney Dickman's clutch master and slave cylinders to go along with the clutch kit. A clutch that won't release due to hydraulic failure is just as bad as useless as one that slips.
