Mekong has more things than Lee Lee's and they give 10% off on your total order, which I love. Lee Lee's used to do this. However, I saw the owner of Lee Lee's work hard all these years and start from a small store on Dobson & Southern. So, my heart is always towards the small business.
Mekong has a large variety of things and the store is packed. It's a bit overwhelming to go there, so you need to know what you're looking for. I wish this store were closer to me, but I'm glad that there are several options for me for an Asian supermarket - Mekong and Lee Lee's.
It's clean and I can't say that the Asian staff is friendly (at least not to me being an Asian), but I found when I ask a non-Asian staff member, they are much more helpful and friendly.
However, I don't expect that I go to an Asian Supermarket for the staff to be friendly, like you would at a Caucasian based supermarket. Probably some sort of double standard I put up with, but c' lest vie.
We don't visit this area of the valley often, but when we do, I try to pick up a few items that Lee Lee's might not have or might be better priced here.