Which rather tends to prove the point that the journey time savings of having a very light and expensive bike are pretty minimal, unless the rider of the light bike rides on drop bars and the rider of the heavy bike is in a sit up and beg position. Commuters and pleasure cyclists (as opposed to speed merchants just trying to go as fast as possible) tend to sit up for the better view rather than just go hell for leather in a low position.
This thread is about the 2 example bikes being ridden to get the most speed out of them. If people choose not to use the drops and not ride for speed as their goal, then the modified MTB with road type tyres will naturally be similar over a flat route with no stops or in traffic for the commute.
My argument is that a light road bike compared to a heavy MTB, being used how they are intended and with the components they are sold with (including tyres), will be faster. It’s misinformation to suggest otherwise.
You’re argument centres around a road bike being ridden like a MTB, half heartedly whilst taking in the views, and a MTB being equipped with road tyres on a flat route without ever changing pace. I won’t argue against that type of comparison, so will end it there.
The overall fact, that we are sure to agree on, is that we should all equip our bikes and ride them how we like, ignore how much money anyone else has spent on their bikes, and enjoy ourselves. Far too much negativity in the world to let that get in between us cycling fans.