Very hard to answer as I doubt many if any will have heard both in identical surroundings, plus I am far from convinced the same plinth thinking suits both equally. I’d also go as far as arguing there are two TD-124s (before you get to any third party stuff), the one with the original heavy ferrous iron platter, and the one with the lighter alloy one. I am a fan of the former and to be honest never really got on with my 124 until I swapped the alloy one out. That is the point the real ease, solidity and rock solid pitch arrived for me. It is the point I felt it really competed with the 301.
The thing I like about mine is for me it sits in the middle ground between say a Linn and a Garrard. It is a nicely refined and detailed deck, but it also has that idler rock-solid pitch, timing, ease etc. It gets right out the way and doesn’t draw attention to itself. It is a very good deck indeed. It only took me seconds to know I much preferred it to to a SL1200G, and that’s a pretty decent bar for a 55 year old deck to jump.
There are many negatives though, they are quite demanding to work on and I’d really only recommend them to folk who have good mechanical aptitude. I enjoy this stuff so it doesn’t put me off. The boutique industry that has built up around these decks will get you a decent starting point at an arguably absurd cost (several charge £1000+ for a service) but by the nature of the deck it will need some ongoing maintenance.
Another thing to bare in mind with my findings is I don’t seem to be a fan of high mass anywhere in audio, so my idea of an ideal Garrard installation is something similar to a Loricraft plinth with suspended top plate and the 301 on its rubber washers, and the 124 in a low-mass plinth like mine or Nagraboy’s using the rubber mushrooms. Mass does something to timing and dynamics I just don’t seem to like, and I’ll trade noise floor to keep what I do like. As such I use these decks in a different way to much current orthodoxy.