I too have a partial NHS top denture and have had them for about a year, and they are great. Previous to this my last denture is still fine (I now keep them as a spare) and they were ten years old. I've worn partials since my early twenties and my first pair were metal with clasps that attached to my back teeth and these were the best, very thin and doesn't cover the whole of the roof of mouth. However, many years later my back teeth had to be removed therefore the only option was the plastic sort. However, I've had very little trouble with them.
If it was me, and the very thin one's with clasps were suitable for you, then I would opt for them.
Saying that the choice is yours of course, but I'm more than happy with my NHS one's and after a few fittings and a few weeks they felt good. I can eat most things with them and the colour matches in well with my own teeth.
Before I had my new denture I had been advised to look into using the services of a Clinical Dental Technician thise guys are suppose to give a much better fit and service but in the end I went for NHS ones.