I tried adjusting the seat height as well to see if that was a factor.
A friend of mine was riding with me when I was on the FX and I was consistently faster than he was. He was riding a Marin Olena. He bought a Trek DS 8.3 and I immediately started having a hard time keeping up with him. He could also go off trail a bit without worry. That's what prompted me to look into them. I thought it would be nice to have a bike I could do non-concrete trails on, but once I started riding it, I found that it was consistently faster than my FX and have gone to riding it primarily with the FX as back up. Now starting to think about trading the FX for a road type bike, but also want to learn more about what makes a one bike faster than another.