I'm considering the purchase of the Ultimate Ears UE-10Pro,
http://www.ultimateears.com/UE-10_PRO.htm or the Sensaphonics ProPhonic
Soft 2X, http://www.sensaphonics.com/soft2x.html

Other IEMs to consider are the Future Sonics MG4,
http://www.futuresonics.com/html/products.html or the Westone ES3,

http://www.westone.com/music/elite.html#es3 but I haven't found too
much information on these in order to compare them against the previous
ones.

As these headphones cannot be tested before purchase, I would like to
know your opinions regarding your experience with these, sound quality
wise.

Ideally, if you have owned both, can you comment on which one would you
prefer against the other and why?