I've never found a great enough difference in chains or cassettes to matter all that much. SRAM, Wippermann, KMC, and Shimano have all served me well. Shimano does not use a reusable link like the others, which maybe a consideration. There are some cosmetic differences within each brand.

Pretty much the same for cassettes except I have used only different levels from Shimano. IRD has individual cassette cogs available if you can't find an off the shelf cassette that suits you.

Brad