Oh but ear length and fur type can have an affect on how fast a rabbit gets warm.
Ever see an Arctic Fox? They have really tiny ears to prevent too much heat loss versus the Desert Fox who has large ears to help cool the animal down.
Also, between my 4 rabbits, none of my rabbits have similar fur types. Spice is very plush with 1" long hair and so much undercoat that his fur sticks out (it does flatten in the summer) in the winter. Zoey has very thin hair but she has a lot of the fine undercoat like feel, very little guard hairs that sits against her body. Reese I'm still trying to figure out but she does have quite a bit of guard hairs. Mocha's hair sits flat against him, he probably has about average amount. Out of all them, Spice gets the warmest the fastest and Zoey seems to keep cool the longest.
Oh and I guess how the rabbit holds its ears can have an effect, a rabbit who holds the ears close to their bodies will not lose heatas easily as one who holds their ears away from them.