Colour: The colour of both drams is about the same at jonquiripe corn (of course, as they use caramel to fix it). Maybe OLD is half a shade darker. The texture of OLD shows late legs and fat sticky tears. NEW's texture is about the same.
Nose: NEW offers a less intense nose than OLD mostly on yellow fruit, malty and grassy aromas. It is slighty spirity and musty. OLD's nose is richer on apricots and other fruits, currants, vanilla, maltiness and some adorable OBF's. OLD is neither spirity nor musty and not grassy. I clearly prefer OLD on this dimension.
Initial mouthfeel: OLD is warming and a little coating (just the tongue) with no distracting moments. NEW is less oily and not coating at all. Guess what I like?
Taste: NEW again is flatter than OLD with a slightly drying and musty flavours profile. Some raisins pop up besides the malty sweet and spicy wooden notes. OLD is richer and sweeter on a nice fruity and malty profile. It offers peaches, apricots and barley sugars in abundance. Again this round wins OLD clearly.
Finish: OLD has a medium length finish with no off-notes or bitter/drying moments. It is very enjoyable on the same fruity-malty profile as the taste. The finish of new is shorter on herbal notes and some drying wooden notes (Do they use some virgin oak casks in these batches due to the cask shortage crisis?). Yes, OLD wins all four dimensions without any question.
The FoSM club voting won OLD by 17 votes versus 3 for NEW (and one draw). This blind tasting showed a significant difference of the flavour profiles and the quality of the spirits (even when discounting any mysterious "bottle maturation" effects on OLD). It seems as if the 12-year Cardhu moved into a grassy-herbal flavours profile instead of the old fruity-malty one (so fermentation time is shorter today - to maximise throughput?). And the newer bottling is less oily and hence of a weaker mouthfeel and finish (Do they run the stills faster due to the whisky boom?). I like the old one as an easy dram to sip but would not buy or drink a new bottling at all...