I have all three 'phones in question. As far as comfort is concerned, both the Panasonic and Sharps are extremely comfy. Except for the music playing, I'm not even aware they are there.
The E2c is a bit bulky.....it is the largest of the Shure canal phones, and unless you use the foamies or purchase the ultra soft flex tips, they can be extremely uncomfortable for some people, myself included. They isolate much more than the Panasonic or Sharps.
As far as sound quality is concerned, my preference goes back and forth between the Shure and the Sharp. The Shure top end is rolled off quite a bit, yet that can be a plus if your music is poorly recorded or encoded at a low bitrate. The bass is decent, but can be a bit muddy to my ears.
The Sharp has a punchier, livelier sound.
The Panasonic, while an exceptional value at under $20, to my ears anyway, falls a bit short in the SQ department. Bass can be boomy and the high end tends toward harshness. I did a direct comparison between the Sharp and the Panasonic, paying particular attention to cymbals. The sound was more refined and detailed on the Sharp, while the Panasonic kind of made a mess out of it. The sound of cymbals with the Shure is also refined and detailed, but it tends to stay more in the background, which, as I said, can be a good thing with some material.
Although they all retail for under $100, there's a pretty big price range among the three phones. If I had to pick only one, it would be the Sharp, although the isolation is not as good as the Shures.
Oh, and the 3-pole, 4-pole thing is unimportant. The 4-pole was designed to work with Sharp Auvi MD units and is supposed to increase separation of sounds. It does sound great on my MD-R7, but I'm not sure if it's the 4-pole thing or the quality of the digital amp inside the unit that makes it sound so good. In any case,, it comes with an extension cable which also is an adapter for 3-pole jacks, so it really isn't much of a concern.
Hope I've been of some help.