It is a close call regarding thermos ultimate 900ml vs the Stanley master vacuum bottle 1300ml
If this is rubbish please let me know
remind us, do you have 1300ml of fluid in the stanley , and 900ml in Mr.T ... if so that does impact experiment quality -
(apart from, personally, not usually wanting additional weight, or 1.3L coffee quantity)
the bigger flask with smaller (to volume) relative surface area/stopper size, should, construction being equal, keep full capacity contents hotter;
if you were able to scale up the T then, they might behave identically.
you could work out the energy loss / Joules, of the fluid in both flasks, and Mr T could be 'superior'. ?
... if you experimented with just 900ml in the stanley, that might be interesting.