Quick summary of my situation. Before moving to Washington a decade ago, I was a frequent mountain biker in Virginia. Lots of mud and dirt and roots and such. I rode a full suspension Trek Y bike at the time (I do miss that silly thing). When I got to Washington in 2002 I bought a 2001 Specialized Hardrock Sport that quickly collected years of dust in my garage. About 6 years ago I put some hybrid tires on it to ride a local paved trail but I only did that a handful of times, then put it back in the garage.

Fast forward to February of this year, after dropping ~80lbs I bought my first ever road bike and I love it. 3,000+ miles under my belt (mostly commuting) and I'm finally able to call myself a cyclist again. With the fall months coming, I am itching to get dirty so I wanna bring the MTB out of the garage and tear up some single track.

My question is simple, are 29er's really a significant upgrade to my old MTB? The Hardrock still rides fine but it's low end for sure (I think I paid $400 for it when I bought it in 2002). I have no problem dropping a grand or so on a new MTB if there is significant improvement to be had over my experience on the 2001 Hardrock I have today.

Any thoughts on what I should be looking for to either a) revive the 2001 Hardrock Sport or b) replace it with a 29er hard tail?