IMO smaller rounded gravel or sand is better for corys than pea-sized. Waste & food fall between the stones making more heavy, dirty work for the cats to feed. The smaller the corys, the more difficult. I have habrosus, only about the size of 2 or 3 peas, I can't imagine keeping them on pea gravel. The bigger the pieces, the deeper the spaces, on sand all is on top.
I really like the look of kj5kb's gravel, but it sounds too big for me. The kind of gravel & sand will vary by regions, they get it fairly local.