I've been using Prophile8 for a week now with my sony wm1a. I must say that there isn't as much difference between them and my er4xr in terms on pure sound quality that I was hoping for. Sure the resolution is slightly better, the sound is more refined, there is better frequency extension on both ends but that's about it. Er4 are brighter and I would say more analytical but still very smooth and enjoyable. The big difference is that er4 are way more in your face, with mediocre soundstage both in terms of width and almost no depth. When I'm applying PP8 just after er4xr they sound almost like headphones that are open back. Sound is bigger, wider, more spacious, very 3 dimensional, less intimate and less involving but more layered and rich. I must say I'm very impressed how it's sounds overall altough I kinda miss the 4,5khz bump from etymotics but there's plenty more to the sound to enjoy. You can add treble and bass with the switches that's great for more heavy music like metal and bass based electronics so you can enjoy these genres too. I would prefer however to have the switch that brings bass down instead of adding more of it. Also I would like that treble can be added not only from 8khz but also from 4khz.
As for comfort I can agree that they are suprisingly comfortable for their size but they are not the best fitting iems that I've owned. Phonak Audeos takes the cake in that regard. I'm using PP8 for a couple of hours a day and there's never a point that I can forget that I have them in my ears and after 4-5 hours my ears are a little sore. Nothing major but there are statements in reviews that these are the most comfortable iems on the market. and in my opinion that is exaggeration to say the least.
Overall I'm impressed both by PP8 sound quality and by how strongly ER4XR's hold up. They have only 1 driver and are over 3 times cheaper. I'm still on the fence If I should keep PP8 or if I should return them. Yes they are great and if someone wants neutral signature and best sound quality they are probably the best way to go hovewer price to quality ratio is just so so. ER4XR can be more involving and their price is just suberb.