Thermodynamics gives the physical size (surface area) of the resistor related to the amount of convection cooling, the lead material (i.e. Cu vs Fe) and diameter for conduction cooling to the PC board.
So when a manufacturer has a magical small size resistor with the same power rating - it's basically bullshit as you can't break the laws of thermodynamics.
I entered the physical size, operating temp, thermal resistance, power at class etc. of many through-hole resistors in a spreadsheet because I am fed up with the game.
For the same power rating, surface area varies almost 5-10x. It's common to order a "1W" part and it's the size of what used to be "1/4W"
Yes materials are "better" and can operate at higher temperatures which is largely driving the marketing bullshit. The IEC tests are in free-air as I also recall, so exploiting that loophole with high temp materials to give misleading ratings. But getting rid of heat, there is no magic there unless you use a fan lol.
Do any of us actually design resistors to operate at say 150°C? It's totally useless to make a board-mounted resistor run so hot, as to damage FR-4.
The Vishay SFR series are the worst in their supermini size and grandiose power ratings. Do the math, calculate their actual operating temp. at rated power. Look at the graphs very carefully.