It depends on how white you want it. Chrystal Avalanche is very bright & white, while White Frost almost has an iridescence to it, so it's a little more versatile.
Crystal Avalanche is one of my favorite highlights for my brow and inner corners. If you use a big fluffy brush (224) it will give you a nice wash of color, instead of a "HOLY CRAP YOU'RE WEARING WHITE EYESHADOW!!!!!" look.
I looooooove Crystal Avalanche. I use it as a highlight for my brows almost every day. And like what ForgetRegret said if you use a fluffier brush with it (I use 227) it's not a super bright white.
I received white frost in my makeup kit - I'm guessing because it's so versatile. If you want something a bit more bold and frosty/shimmer then you'll love crystal avalanche.