Wouldn’t you be able to get a r5 1400 for the same as a 8100?
cheapest best is h310. b series has extra ram slots, m.2 slot, sata ports. so it's not cheapest best, it just has extra features that most of budget builders don't seek. most of people claim b360 boards are best, because the price difference is low, but it's not true in all the countries.