The MS 200s sounded more open than just about every other under-$400 in-ear headphones I've ever tried. Returning to in-ear headphones after listening to the MS 200s, you can't help but notice how the sound is smaller, more stuck inside your head. Another plus, the half-in-ear design doesn't seal you off from your surroundings, so you can wear the MS 200s when walking or exercising and still hear cars coming. The downside to the design is that it lets in a lot of noise, so if you crave isolation, go for noise-reducing or conventional in-ear headphones.
I didn't have any higher-end earbuds on hand, but a comparison with standard Apple earbuds proved the MS 200s' superiority in a hurry. The Apple earbuds' sound is so bass-light, it's anemic. Voices also sound thin and the higher frequencies are fuzzy and crude. It's the headphone equivalent of listening to a cheap table radio. Switching over to the MS 200s, the sound blooms, the balance is much richer, and there's clarity, plus you hear the sort of large and small dynamic gradations that were completely inaudible over the Apple buds.
That wasn't close to a fair contest, so I compared the MS 200s with a set ofin-ear headphones. The MS 200s' bass may be full, but definition isn't a strong suit; the S4s' bass is just as full, but much more detailed and natural. Cymbals sounded more realistic over the S4s; the MS 200s' treble sounded a wee bit harsh on some recordings. The S4s' sound was clearer, more immediate and present, but spatially smaller and more confined than the MS 200s'. That's why I found the MS 200s' wide-open sound easier to listen to and less fatiguing after hours of use.
These are two very different-sounding headphones, and I liked them for different reasons. I enjoyed the MS 200s most when walking on the streets of New York City. While some people like to seal out ambient noise on the streets, I personally don't like feeling too cut off from my surroundings, so the MS 200s were appealing.
The Phiaton Moderna MS 200s may look a little like in-ear headphones, but they don't sound like them. Like earbuds, they don't seal you off from the world outside, and the sound is more open and spacious than that of most in-ear headphones, which will appeal to folks who don't like the intrusive feel those can have.
The downside to the MS 200s is that the sound feels less direct and immediate than you get from a good in-ear design. But these are versatile headphones that will appeal to folks who want in-ear-style headphones for day-to-day use as well as for exercising. At $120 online, they're reasonably priced, but I think Phiaton could get more traction with a $99 price point.