I have owned the Zero Audio Carbo Tenore's for about a month, and it is safe to say that these are some of the best bang for your buck headphones in terms of sound quality I have ever heard (and I'm obsessed with finding good cheap headphones). HOWEVER, the strain reliefs on them are abysmal and the sound already cuts in and out in the time I have owned them. I, by no means, am aggressive with my headphones, but the right angle plug is one of the worst plugs I have ever used. The main problem is that I put them in my pocket. That may seem like a decent place to put them, however the right angle connector is so weak, that when it gets pushed up it puts strain on it, resulting in sorrow.
So I just ordered a pair of Vsonic VSD1S's. Eagerly awaiting them. I'll let you know what I think.
The sound quality of the Carbo Tenore outmatches the VSD1S by quite a margin. But the build quality on the Vsonic is much better. It really all comes down to if you want to spend $40 on the Vsonics, or $80 dollars on both after the Zero Audios break.
I owned both Vsonic's and Zero Audio's and have a different experience. Beyond personal taste, The Tenore's are more "in the face" with great timbre but quite tiring for long sessions.
The Vsd1S's are smoother sounding, more relaxed slightly V-shaped.
Depend on the recording, but for one-fits-all I would recommand the V-Sonic. They are a little less revealing and can deal with all kind of recordings.
I must add after a week testing the VSD1S (the new version with straight plug) The microphonics on them are not far from being unbearable ! I just can't wear them when walking and as they are not built for the cable to go over the ear, no walking the the dog with them... too bad