there are a lot smarter guys than me on here...
other than forks, i dont think there is a lot of difference between those 2 years. the 01 should have 43mm and the 04 should have 45mm..
both are good bikes. i have an 01 that has been a great bike.
parts are no big deal, the bikes are awesome, the knowledge and willing to help on here awesome..
price and condition... there are some extremly nice older gg's out there. i would venture to say my 01 has less than 100 hours on it, it was brand new when i bought it in 08.. good luck with your choice and let us know what you get..
and welcome..
jay