As a small "buyer" and occasional seller, I lean to those where I can get all my odd parts at once. Most important to me is to just have an all in shipping price. I HATE being nickeled and dimed with this fee and that fee and this PayPal fee, and the dinner fee, and the purple brick fee. I will shop somewhere else to avoid it, even if I pay a bit more instead of using two sellers. If you build the costs into your parts, it should work out fine on the long run. Yay LEGO!