Salsa knee to knee

I used to dance a lot on 2, mambo step: you start on 2, going backwards.
There is not much difference with dancing on 1, just start a little bit later ...

Then I heard that there was a different style, on2 starting on the first beat which is slightly different
and not that easy to spot. The real difference is not that the steps are different, the breaks and pauses just fall on different parts of the beat.

Now dancing on 2 becomes even more complicated. When both dancers, men and women dance on 2, but not the same style, .. it feels akward because you bumping into each others knees.

A song was starting and he asked her to dance. She said yes and they locked bodies in the semidarkness.

Then they bumped knees. Then they pulled in different directions. Then the song became interminable. When it was over, they spent time talking but did not dance again.
...
Ms. Shanley was dancing ''on 2,'' known as New York-style mambo, in which the first long step, known as the break step, comes on the second beat and there are no pauses. Mr. Lopez was dancing ''on 1,'' the style favored by many mambo dancers in which the first long step comes on the first beat, and the dancers pause on the fourth and the eighth beats.
Battle of the Mambo Is Bruising Some Toes

But in the end it really doesn't matter:

During my short time in the fabulous world of Salsa, I have grown to realize something. Dancing Salsa On2 is not necessary better than dancing on On1 or vice-versa, but dancing On-time is always better than dancing Off-time. Yes I still prefer to dance On2, if the option (honestly) presents itself. However, I have learned to feel the music regardless of what beat I break on.
Salsa on 1, on 2 or On Time