I will buy anywhere with only two conditions- seller is legit and they offer good price.
Amazon offers (usually) better price and free shipping + no tax.
macmall offers deals, paid shipping and tax, but you can usually get that back with rebate. Rebate comes fast. However BEWARE of third party rebates. It is 6 months after I submitted rebate for PC USA usb charger(for ipod nano) and I got nothing. It says "processing". I think it is a scam and will never buy any third party stuff even it is "free" from macmall.
anyone wants to add more to this list?