I popped into Jaben yesterday and the JVC FXT-90 and Radius TWF21 were available for demo there. I bought the JVC Limited version since they were the same price as the black version (SGD $248, yea not cheap I know, but my ears were itchy). Here's a picture of it.
I will start off with the JVC FXT90 first. All listening was done on my Sony Ericsson Arc phone.
Design and Comfort:
The red part where the JVC letters are seems like aluminium to me. The surrounding and wire relief is made of rubber. The rest of the earpiece are made up of hard plastic. The cord for the limited edition is made up what I think is some red wire casing that goes around the actual wires that carry the sound signals and encased in clear plastic/rubber tubing. The wires are quite soft but has a tendency to get entangled as they are not buttery smooth like better cords from other manufacturers. The chin slider moves up and down very easily, maybe too easily. The drivers crinkle when putting the earpiece inside my ears, so I think there are no vents on the housing. The fit is very comfortable, and the shape of the earpiece acts as some sort of pseudo customs which provides even more isolation, and combined with the rubber sleeves and lack of vents, the isolation is above average for iems with this type of design. The earpiece do not protrude out of the ears that much, unlike the Radius DDMs.
Treble - Highs are nicely detailed and crisp, without being overly exaggerated like etymotics or re0. There is no sibilance here.
Mids - Mids are good as well. Not too forward nor in the background. Vocals sounds realistic without sounding nasal.
Bass - The bass falls a bit short here. There is not much sub-bass nor does it extend very deep, so there is no rumbling epic feel here. There is some mid bass, which makes the overall sound a tiny bit muddy. Don't get me wrong, the overall sound is still pretty clear, just that in music where there is a lot of bass, the JVC tends to get a tad overwhelmed.
Soundstage - Left and right is quite good, but does not sound spacious. Music is pretty much in the head.
I have only heard the Radius TWF21 in store. The impressions were similar to when I heard the TWF11. Smooth sound, spacious soundstage, but IMHO, lacks the focus on highs which I like. This also makes the sound slightly veiled to my ears. The TWF21's design are improved over the TWF11, but still feels weird to me as it sticks out too much from my ears. In the end, I bought the JVC dual drivers as I like them better. If you like the TWF11, I'd imagine you will like the TWF21 too.