OK, this is a very interesting subject, and I've read through all the posts (for the most part). I love physics, and I love teaching. So I can't help but give it a go here.
First we need to take the subjectivity out of the question. That is, the word "better". Now let's examine two hypothetical air frames. They are both made out of the same material and are identical in every way, except that air frame B is half again the weight of air frame A. So, if air frame A is 20 grams, air frame B is 30 grams. Now for the motors. They are weightless and the variable property is power. Now you see why these planes have to be hypothetical.
So with zero wind, will plane B require more or less power to take off than plane A? What about to stay aloft once airborne?
I think we can agree that plane B will require more power to fly than plane A. Also once in the air, it will not be able to perform exactly like plane A because of momentum. Momentum is Mass x velocity. So if we provided plane B with just enough power to match plan A's speed, plane B would always have more momentum.
Scenario 1: Both planes are flying in a parallel formation and come in for a landing. All other variables are the same, touch down, throttle cut, etc. The only forces acting on the planes at landing are gravity and friction, which are equal and constant for both. Which plane will come to a stop first? Which plane will roll farther? Plane A will stop first and plane B will roll farther because it takes more force to influence an object that has more momentum. That's basic physics.
Scenario 2: Again,both planes are flying in a parallel formation, and both are suddenly hit by a 5 MPH gust of wind exactly perpendicular to their flight path. Because it takes more force to influence an object with more momentum, which plane will be more influenced by the sudden gust of wind? Of course plane A will be influenced more by the gust of wind because it has less momentum than plane B. That's physics.
Plane A and plane B will perform differently given the same set of circumstances. Now keep in mind that these are hypothetical planes. In the real world a plane made from heavier material would probably have a different airfoil as well as a more powerful motor, which probably adds more weight. And because it requires more force to influence how it flies, it will probably have larger control surfaces, etc., ad infinitum.
The whole question about one plane being better or worse, is based on the pilot's expectation of the performance. Some, like earthsciteach will prefer a lighter plane with enough power. I don't think I could handle that same plane in windy conditions as well as earthsciteach could, so I would prefer a plane that is less susceptible to the effects of the wind. The plane that would be "better" for me to fly may be a heavier plane, not because it performs better, but because of my skill level.
So how's that for a very verbose, politically correct, diplomatic non-answer?
RB