I like dealing with HLJs support more because there isn't as much of-if any- language barrier. They're easier to cancel orders with. Their prices are higher but you can get lucky with sales and their shipping is cheaper. Amiami generally has lower prices and more special/limited items though. I've used both and haven't had bad experiences thus far with either.
I'd go for whichever store has more of what you want being released in the same month so that you can save on shipping.