Agreed. For a suit that's going to be worn in the summer, I'd rather go with linen for either color - they look better in that fabric IMHO, so why not?For a fall/winter suit, brown worsted or flannel is fine.
My next NSM suit will be in the single breasted peak lapel (SBPL?) cut. I'll be using a dark, dark, almost-charcoal, brown chalkstripe worsted, 16 oz., from the P&B Universal book. Two buttons, no vest.