The Westone 4 sounds basically the same as a Phonak PFE with grey filters. It just needs three additional armatures, and a MSRP of $450 instead of $150. Now there are some ultra-nano-tiny differences that should be more or less irrelevant for regular listening, but they really do sound the same, all in all. There's a tiny bit more treble resolution in the W4, a tiny bit more treble sparkle in the PFE. The W4's bass rendition is a tiny bit more voluminous, yet the PFE reach down lower than the W4 and are a tiny bit faster. PFE have a tiny bit more overall clarity than the W4 - both have similar (excellent) dynamics and similar stereo imaging. All differences are however so minuscule, only apparent in a quick switch AB test, they should not matter for real life purposes. The difference that probably does matter is that Phonak managed to create that sound with a single armature for $150, while Westone needs four armatures and a price tag of $450 to achieve basically the same, some two years later. By the way, James444 heard both side by side as well, and he seems to generally agree with that assessment of the W4 vs. the PFE.