mundorf m-resist supreme vs jantzen mox and others

More Burn in time needed. Different room, speakers, gear, ears etc... all play a role. 

so, mills mra need more burn-in time ?
does resistor has burn-in time ?

Yes, they both will change over time. Resistors certainly change over initial burn in time of say 60 hours...

Mills is my go to resistor also... I've tried several,  there are clear differences in resistors,  but to my old ears,  not as much as in good capacitor difference....
"Hot"  means a peak,   normally a slight peak,  in the upper midrange to lower treble region...
just as "Warm" refers to the same in the lower midrange. 

@timlub 
do you tried mundorf mresist supreme ?