Are NBS cables are sound better than Nordost ?

It's better to judge the right type of cable depending on the quality of your system. Many people make the mistake that they think the most expensive cable is always the best for their stereo.
The "big" NBS cables and some other serious brands only work when the execution of inner and outer dynamics of your components are extremely well organized.
Otherwise the sound gets too flat or dry and the flow is gone; then the cables are letting you hear too much information.

I have tried a lot of cables in my system and when I tried some of the higher-cost NBS cables there was no way of going back. The NBS have an immediacy, a vividness in the midrange that is to die for. I was surprised at how much bigger the soundstage is and the improvement in bass. The only problem you might have, if your system is bass-heavy to begin with, the NBS may enhance this effect until you get too much bass. Not a problem in my rig but it might be in others.

NBS cables are expensive, there are other brands just as expensive. How many companies give you full credit to upgrade their cables or trade-in for the latest version? If you like the sound from these cables, then it is a good deal in the long run.

Truthfully, there is no way to judge cables except to borrow a pair, install them in YOUR system, and evaluate it for yourself. Nordost is beautiful, but the Valhalla's tend to be a little light sounding. They are fabulous with some euipment, and not quite so on others. Price should mean very little in your quest for cabling. Check out Anti-Cables on this site, or go directly to Anticables.com to look into this stuff - very cheap and excellent. I have a statement system and use this stuff.