I can tell the difference with this XO marmite.
Trouble is I find it lacklustre, like the Guiness that preceded it, but much more palatable than the Champagne Rhubarb (mouldering away in my larder ...which is unheard of).
It's just not as defined or robust as regular marmite, that if you have grown up wiping toast on a jar of marmitey goodness doesn't have the same kick.
Ok the taste is multi-layered & is (imho) brought out more with butter compared to marge, however it is also LIKE comparing butter to margerine as well, something distinctly unfulfilling.
Stick with the original & the best, ignore the rest!
(are marmite trying to divide & rule even marmite lovers now? ..if so a step too far.