The factory hubs are at best 13 years old. Aisins are nice hubs. Don't get me wrong. However by now they're used and abused, maybe rebuilt...even more maybe rebuilt correctly...I've had several sets on several different Trackers that were messed up due to improper maintenance and/or no maintenance. The set I had on the '03 GV I spent $50 after being told they were in great shape. They visually appeared decent but the inside looked...well...used and old. Everything engaged fine and worked so I just installed them and they worked for a year and change. Then they locked up solid. Not having the time to remove them and learn how to rebuild them I just sprung for a set of Warn's from Rocky Road.
The Warn's are typical Warn quality. All metal, no plastic (well, I think the trim might be plastic). You don't need the special conical washers. Full 3/4 turn to engage them. O-RING SEAL (I never could get the Aisins to seal up correctly). Lastly...THEY WERE NEW WITH A WARRANTY. No worries about someone's crappy work rebuilding them, using too much or not enough grease, rusted parts, age related wear and tear, etc etc etc.
Also from previous experience across several different vehicle brands (GM, Ford, Suzuki, Toyota, etc) I've yet to see anyone really prove that Warn's got a superior competitor except maybe a NEW Spicer or Aisin hub and good luck finding either for any application anymore. I've also seen Mile Marker, ProComp, Superwinch, etc's el cheapo hubs fail in a variety of applications in situations that they shouldn't have. If you make a Warn Premium fail you're either wheeling hard or hitting it directly with something very hard.