Can anyone tell me whether Sine is better or Mobius?
This is a very difficult question. I've owned both and overall liked both, but each have their drawbacks.
What Mobius does better:
Much better fit:
Some people just say that sine is uncomfortable. I agree, but I can definitely use it for about 2 or 3 hours without much issues. The bigger issue for me is getting the seal, and making sure to put them on properly. If you force them on, you could develop driver flex pretty easily.
Mobius fit is not bad, the only annoyance is it's heavier and looks much bulkier.
Soundstage/Presentation:
This is more a matter of taste. I personally prefer the "bigger" presentation that mobius has with the 100mm drivers. Due to sine being on ear, the presentation of the music is more "focused", but I can see people preferring this.
What Sine does better:
Detail:
I have a theory that Sine and Mobius are actually similarly detailed, but Sine's form factor as an on ear headphone makes it appear more detailed. A tighter bass response also helps with its clarity.
Longevity:
Supposedly Audeze will offer battery replacement with the mobius. But outside of that, once your mobius dies, it becomes useless. There is no passive mode at all. A lot of Sines have lasted for years, but some do succumb to issues.
Driving/Amp:
Sine gives you the option of using the included cipher or your own amp source. In my opinion, using a better amp setup does improve Sine hy a decent margin. Mobius amp also suffers from a slight white noise/ hiss. This pissed me off when I first got it, but I've since come to accept it.