Well I guess exactly what you said, they sound warmer which counteracts the steril newer stuff most the time. Very detailed, deep quiet, bass is all there.. And they normally run dead silent in comparison to all other tubes I have had.. Yes JJ's actually are one of the better new tubes, I had them and found them nice, they hummed a little, most of the mullards were a little pricey and matched, tested for microphonics and were all dead silent, literally with 101 db efficient speakers you would never know the units were on they are that dead quiet and always sound smooth,even in 60 db phono stages. Don't take as long to burn in, faster to warm up and sound right, normally about 20 mins and they are at most of the peak after about 50 hours first. Maybe I just like the character and consistent quality of the mullards, others have always given me problems and not always sounded the way I like. Thats all I can explain, however don't take my word, many, many people will consider mullards especially in the 12 series tubes some of the best, but maybe not if they don't work for you. Its up to you to try.