I 100% agree with Medgal's analysis!
The AWQ is a little more versatile overall, because there's a little more variety between the shades - nude/mauve/white/black-ish. None of the colors really read "grey" the way all the colors in RS do, though.
The lightest in RS is not as bright as the white in AW, it's a pale grey that is not bright or reflective at all - it makes a really excellent brow bone color for a grey eye look for people who don't look good with a bright or very contrasty color on their brow bone (like me!!!).
I bought both, and I rarely buy quads, because taupe (AW) and grey (RS) are the two colors that are super fussy for me around my eyes and usually look too cool. If you're trying to save money, have typographic and some other greys you like already, you probably can skip RS, but if you love grey and are always bummed because they never look that good on you for being too cool, the RS will be really satisfying. I basically feel like I don't need any more grey shadows at all now - my needs are being taken care of.