Every full set comes with 1 rare, and there are 87 rare cards in the game minus 10 leaders and 4 CRs, so that's 1:73 chance of getting it buying a full set.
The Danger pack has 98 possible cards (excluding CRs) but you can buy 2 1/2 Danger packs for the same price as one Full Set so that's a 2.5:98 chance if I remember my math correctly. Seems like better odds to go with Danger, except since Rares get less distribution than Commons and Uncommons the odds of getting a Rare in a Danger pack are actually a lot lower.
I'd say 1:73 is the best you'll get--go with a Full Set. Even if you don't get Vickie you'll at least get another Rare you can sell on the market.
full pack is horrible. they force you to buy using 50 credits and you only got 1 rare cards (maybe that rare cards is cheap rare cards, for example, leila, corrina, etc)
danger pack has higher chance on getting many good rare cards, kolos, vickie, jackie, kenny, grasmxxt, etc.
Well, you don't "only" get one rare with a full deck, you are certain to get AT LEAST one rare, but I'm pretty sure I've gotten more than that in some of the full decks i've bought. I picked up Kolos from a full deck in fact. And Kiki and lelena. If they hand out Rares in the Danger pack at the same frequency as Commons and Uncommons, then you are right Danger is the better option. But if Rare means that fewer of that card is distributed, then the odds looks better for the full deck--that's not me, that's the numbers speaking, your own personal experience may vary. I personally think I only once got a Charlie from a 20 clintz pack, most of the time its a whole lot of Cell and Brutox and Oryon...
Rares are not meant to be distributed like commons and uncommons, so its only natural tht there are less chances of getting a rare from teh danger pack compared to getting a full deck. but if your looking for a specific rare, u have more chances of getting danger, action or cool attitude packs compared to getting a full deck.