Trek and GF both great bikes. I think I would go with a leftover 2009 bike over buying used. The two you have listed for around $600 will get you a lot better components might be the way to go if you plan on riding often and the bikes fit well.
go test ride the rockhopper if u can and trust me u will be in love with it and at the price its a steal as long as there are no major problems:thumbsup:OhioriderAaron said:I did get an email about a used '09 Rockhopper Comp for $650 with some decent upgrades, so I may have to look into them also. Seems like they have a good component list for a great price!
I also got an email about a used '07 or '08 GF Tassajara Disc.