Earlier quoted context omitted.
Strange, it runs just as fast as Chrome on my 2013 MBP
It seems to only happen with certain Retina MBPs. Which is a shame - I really wanted to like Firefox on Mac.
On those same pages, Chrome and Safari work just fine.
If Apple were making MBPs better each year instead of demonstrating their "courage" ("This time we're taking X away from you because as long as Windows is the only competition, whaddya gonna do about it?") I would have already bought a new one, and that would presumably have more powerful graphics and not get as hot, but I would still want to verify that FF wasn't running the battery down faster than Chrome or Safari.