The vast majority of energy on a bike goes to aero drag, and most of that is the rider. Are you in a more aero position on the Merida? That would fully account

The vast majority of energy on a bike goes to aero drag, and most of that is the rider. Are you in a more aero position on the Merida? That would fully account for it. The difference in weight is not capable of causing much difference on flats, since it would just slightly increase rolling resistance. The differences in mechanical efficiency of well-tuned road bikes is also pretty negligible.