My 400ex will go anywhere. Parts are cheep and everywhere. They are easy to work on.
The 01 raptor has big issues with 2nd gear. If it has not been corrected you will have to split the case to repair. Many dealerships will not work on models that old. If you dont have the knowledge, tools and time to take on a project like that pass it up. If the owner claims the 2nd gear issue has been fixed ask to see paperwork.

 

i would for sure go with the 400ex, the 01 raptors had tranny and clutch problems and ive also heard about bad a-arms, everything i read about 400ex's is good besides the fact that the older ones dont have reverse. Another thing, you cant beat hondas reliability.