I'd been planning on going to Cardiff again this year and was looking forward to it. To me, it had the right ingredients with lots of places to eat, shop and stay right there and an amazing atmosphere and you could make a weekend of it and all on the doorstep of the stadium.
I've had a look at Google maps to see what is around the NSS.....and it is pretty barren for an event place (lots of houses though) and with a severe lack of hotels, shops and food places (and a piddly train station that I am not entirely sure is wheelchair accessible). Unfortunately, this means that to attend, it will be buses, taxis or walking miles just to have the same amenities and when you are a wheelchair user, I can tell you this is a major pain in the bum, exhausting and stressful.
Travel time for me is pretty equal, however at least Cardiff station is right there and not a few miles away for the mainline as it is for the NSS or piddly like the closest one to the track.
It may or may not have better racing (it all depends on what the weather does that weekend), however without the easy access amenities and the loss of the atmosphere before and after the GP because of this, it is a no from me.