That is a question that has been asked so many times and there are many threads concerning that.
It is also a very good question as you want to know which one to use on what occasion or which one best suites your personality.
Now when the ladies first starting discovering the differences we first realized it had to do with personalities.
Instant sexiness/A is for a more aggressive type Angelina Jolie type girl and B is for someone who is more girly and gentle like Marilyn Monroe.
Instant sexiness/A or B seems to have a not so good reaction on persons who use it and did not properly match their personalities. From reading the forum I find that this is only a handful of women.
Instant sexiness/A makes you feel confident and sexy and because of that you start to act the part and men are drawn by the vibe you give off.
- I am woman , hear me roar*
Instant sexiness/B does not necessarily make you feel sexy but gives off that sweet girl next door type of vibe and this sends the Alpha male wild.
Most of us like myself tend to use both of these not because of personality but because of the vibe we want to give out at the time.
For your first try I suggest you get the sexiness that matches your personality and when you get comfortable with it you can try to see if the other can be used to lure those fox to your side. 