Are we trying to do a simple weight vs average journey time comparison here, or are we introducing other factors also? You seem to be coming at this from the standpoint that road bikes are naturally better because they are lighter, have lower rolling resistance tyres, and offer a different riding position. However, you can only maximise those advantages if you ride a route which allows you to get full speed up without the risk of bike damage or coming off. My guess is that if all three bikes were ridden over both routes and an average speed calculated, the differences would be greatly diminished. The full-sus would likely gain a couple of mph on a smoother road and the road bike would lose a couple of mph on the track route, but it would make less difference to the hybrid. It would be interesting if meta lon actually did these 2 alternative routes on all three bikes and then posted up the journey times.