I had some of the Leggings and hated them -- they compressed my kneecaps and crushed my calves. Conversely I have two pairs of the Always Skinny, which I sized up one size on and I love them. I have them in grey, just bought a pair in white, and will probably get a blue pair when my current skinnies die.
The Always Skinny are more substantial than the Legging jeans, and while fitted, have enough body to stand on their own. The legging jeans do not size up well, the thin stretchy fabric ends up looking like melted skin or something.