Pros: Smoothness, unique flavors
Cons: None (cost?)

Tons of people say that all vodkas are the same. And they're wrong--either because they have not done head-to-head tastings of straight vodka or because they shouldn't quick their day job to become a taster.

That said, I believe that one's favorite vodka tends to change in the way that one's favorite wine changes: with more tasting and with increasing willingness to pay a little more. And the challenge of describing the change is that not only do "good" qualities come with superior vodkas and wines, but "bad" qualities decrease. For years, I found that Stolichnaya was a favorite. It was easily available and smoother than most when served cold and neat. Then I tried Stoli Gold (in those days, it was called Stoli Crystal). What a change! Flavor without burn.

And then I found Ketel One. It is a great selection for sipping frozen, straight vodka. The smoothness and softness difference versus Stoli Gold is not as great as that between Stoli Gold and regular, but it remains quite pronounced. The alcohol in Ketel One comes through in a slightly medicinal way, but I mean that in a clean, pleasant sense. It doesn't express itself with noticeable additional taste--which some vodka definitions actually require. Ketel One is a great addition to any freezer and I still order it. But then...

...Grey Goose ran an interesting ad. It showed a set of review scores for vodkas with them on top. No surprise. But what I found interesting was that the ranking in the scores for the other vodkas was exactly the order with which I agreed. Since that seemed to indicate a review standard that fit my taste, I tried a bottle. And it is indeed the best vodka I have tasted. But it is also a different style than Ketel One. First the similarity: GG and K1 share the extreme smoothness, having flavor but none of the alcoholic burn of lesser spirits. But GG adds a light floral, herbal quality. You notice this even in the smell--with a slight juniper sense almost like a gin. (Which can't be too strong because I don't like or drink gin!) And the herbal flavor is a nice addition. I should stress that this herbal flavor blends into the overall sense of GG without being extremely noticeable or tasting like a "flavored" vodka. When tasted alone, I don't notice it strongly. But when tasted head-to-head against K1, the addition is clear.

My concluding recommendation is that you need two bottles in the freezer.