On my bike, I use the $6 KMC 6-8 speed chain that available for $6 at my local "sports & more" store. I bought a couple spares for that price. One reason was that all the links/pins match for sure. IF I need to lengthen/repair, I know I have a length of old chain I can use IF needed.
I don't have 9 speed stuff, but the way I understand it is that you don't reuse pins on them.