I have heard both but I would not buy either. I can’t really comment on the small difference as it was a quick demo due to me not liking them
I think the 804D4 is one of the best looking speakers but they would be hard to live with. They are detailed but very sibilant with female vocals and thin on bass. The sound stage was deep and wide though. I would look for a used pair or 802/803 as they are much better to my ear in all area. If you need a small slender speaker the Revel 226be is much smoother with more even dispersion than the 804 and can be had for 1/3rd the price if you shop around. If you want a good looking speaker I would check out Sonus Fabers current stuff. The new soneto looks real nice and the Olympica line also sounds more balanced than the 804.