The Dali IKON are definitely better than the Dali Zensor, but they are also more expensive.
The Dali Ikon 2 are about $640/pr.
The Zensor 3 are about $299/pr.
But indeed the Ikon are better speakers.
The Zensor 3 has a 7" bass driver with response rated at 50hz at -3db.
The Dali Ikon 2 have a 6.5" bass driver with response rated down to 41hz at -3db, and the Ikon have the additional Super-Tweeter.
If you can afford the Ikon, then definitely get them.
There are plenty of good speakers out there in the range between the Zensor 3 and the Ikon 2, you just have to set your budget, and we can recommend several good speakers to consider.
Is there a reason why you have picked DALI? Do you have a dealer nearby? Nothing wrong with them, great speakers, but not the easiest to find for an audition.
Though of limited value, and very much dependent on the speakers you are listening on, here are the Dali Zensor 7 and another video form the same person playing the Dali Ikon 6.
The Zensor are very smooth and clear, but the Ikon are clearer and have a more crisp presentation due to the Super-Tweeter.
Given that YouTube compromises every video, the difference between them is going to be subtle, but if you focus on the highs, and if you are listening on decent speakers, you should hear a difference.
This person has Four Ikon 6 videos and Two Zensor 7 videos -
Dali Ikon 6 MK2 Playing Renaud Garcia (really stunning) -
Dali Zensor 7 playing Kenny G -
The Zensor 7 are still very clear, just not as clear and crisp as the Ikons.
So, if you can afford it, and you don't mind spending the money, then certainly, the Ikon 2 with a crisper more present presentation and deeper bass response are the right choice. But, at least in the UK, they are twice as much money.
Steve/bluewizard