I would caution against trying to compare such measurements without careful comparison of all the factors involved. For results to have any meaning, you need to look at the total impedance curve of the driver in the test box. Then you have to look at the spectrum of the test signal.
For a simple driver in a sealed box, you will get the worst case power compression driving a sine wave at the Rmin that falls above Fb and before the inductive rise, or at really low frequencies, but there you have to watch out for over-excursion. You will see the best case for this sealed box example when driving a sine wave at Fb. If the two drivers have the same in-box Fb, and have similar thermal characteristics, the driver with greater motor strength will have less current through the voice coil at Fb.
Let's remember that it is in fact current through the voice coil that causes heat. More specifically, current x Re (or Rdc) of the voice coil is what defines heat. So when the impedance peaks, current goes down, even though voltage is the same.
In the case of a vented box, the worst case is at the tuning frequency. Here there is both an impedance minimum as well as a minimum of driver excursion. Of course as that port starts to choke off, excursion and impedance goes up. Call it thermal protection by distortion.
It's also what many amplifier manufacturers expect and design for to maximize power. If you design a speaker with a minimum of compression and non-linearities, make sure the amp power specs are relevant to your application.
In a horn, where we see often a rise in impedance over a wider band, it should come as no surprise that thermal performance will be better.
Personally, and especially while peaking over Tom Danley's shoulder, I've come to realize that while some drivers do behave much better than others, power handling is much more indicative of durability to abuse and how bright you can make the voice coil wire glow with the crazy amounts of power we have available today. Of course once you get past about 3dB of compression, additional average power really doesn't do much for you. If you keep going deeper with the investigation, you will probably find that box design and appropriate driver parameters give you a much bigger "lever" on the thermal capabilities than driver construction. After you maximize that aspect, then you just need a driver that can withstand the level of "abuse" you expect to dish out.
My 2c.