First off Red Gard is thinner in consistancy and harder to get the desired thickness. Second you don't have to use fabric on your pan and changes of planes with Hydroban and AquaD, you do with RedGard.
And last but not least RedGard is very Pink
when applying it to the wall and I don't like working in a pink room
Jokes aside on the color though, that is also one thing I don't like about AquaD. It dries a very dark green and can make it hard to see in some showers, and hard to see pencil lines pretty much everywhere. It is still my go to liquid though because of availability and price over Hydroban. I just use red wax carpenters pencils for my lines, and work under lights if I am in a "dark hole" of a shower.
I have never used Red Gard for a pan, but I have heard stories (on here I believe, but don't have hard evidence) that it has reemulsified when doing a flood test.