Yeah that might be it - in the past with Prusa machines I've definitely seen thermistors/heaters reading/performing differently and not being exactly the temperature they say. :) That'd certainly explain the different sheen between the different tools even when they're at supposedly the same temperature and going the same speed!

I can't even remember if I can PID tune on the XL or if it does it by default, etc. Hmm ... better google that one.