I've heard both and consider them both to be very good.
How you describe the sonic differences is an odd exercise.
The Diluceos seemed a bit more dynmaic and played at higher levels better. The 1801 original and B version is very nice. The upper bass is improved. The Diluceos have a bit better upper bass. That Critical Midrange??? maybe a nod to the 1801....upper midrange perhaps a nod to the Ribbon, perhaps....very tough call.
I'd be very interested in comapring Veracity Speakers.
On a side note....I am about to delve into a pair of Dan Wesnor's Ella speakers.
If we can I think Bob is taking the Diluceo down to Seattle for the DIY event with the Criterions as well. I will have my van loaded with up to 14 sets with subs i am taking to the event.
So at that time the Diluceo will be at the same location as the 1801S.