Hi Barry. My experience with these tyres is on TSRs and not NSs (sadly!). This is also personal preference.
I had some folding bead Stelvios in the past, supplied with a second hand TSR I bought. I found them puncture prone. Worse, the sidewalls appeared fragile and easily damaged. Having got only a couple of hundred miles out of the pair I mounted, the other three I had joined them in the bin! I haven’t had any similar experiences with wire bead Stelvios and Duranos, which have both coped well in the urban commuting role in which they have mostly been used.
I’ve done it now, haven’t I? And it’s the 13th…
Hope this helps. David