Both Jon Renau's 101F48T: Martini and Raquel Welch's RL19/23: Biscuit look very similar, but are actually very different.
101F48T: Martini is a gorgeous light brown blended with grey and ash/platinum blonde tones throughout and is definitely going to be the warmer of the two. You can watch Heather's color spotlight on this shade: HERE
Now, Raquel Welch's RL19/23: Biscuit is actually a medium blonde/sandy ash brown base with very light blonde (almost platinum) highlights throughout. Raquel Welch's colors are generally more dynamic than Jon Renau's, so the highlight will be more prominent.
Heather actually doesn't have a color spotlight on this shade, but you can watch there great review where she really breaks down the rooted version of this shade: HERE (The rooted shade is exactly the same as the un-rooted version.)