Originally Posted by
fuji86
And by that, I've ridden the same 30+ mile loop with all 3 bikes, the atb keeps me out riding the same distance longer ... no doubt pushing all 3 bikes just as hard, the atb will get me into better shape.
This discrepancy is solved by not limiting yourself to riding the same distances.
If you push yourself just at equal efforts on a MTB vs a road FG, the FG will go faster. You're doing the same amount of work, just covering more ground.
If you do either for an hour, you're getting the same workout, you'll just have gone farther on the FG than the MTB.
Pick the one you'll have the most fun riding, because otherwise it's entirely a wash (unless you're interested in singletrack or real MTB type riding, which I'd posit is a better full-body workout than regular road riding).