I used to have a Klein hardtail MTB that I rode with slicks on the road at times. It had a suspension fork with lock-out. On the road, it was amazing how much the fork would slow me down if I didn't lock it out. It was as if someone had put the brakes on. But even with a fork with lock-out, you are still hauling around an extra 2lbs with a suspension fork. So go with the rigid if you are going to be riding it mainly on the road. At present, I even have a rigid fork on my MTB. As long as I keep the tire pressure on the low side, it rides fine without suspension, though I don't do any rough trail riding, mostly railtrails and unpaved roads.