I switched to Yaz from Yasmin this summer and am thinking of going back to Yasmin. (or quitting altogether, but that's another post
)
Yaz spreads the bcp hormones out to 24 days instead of 21. What that means for me is that my PMS symptoms still start at the beginning of week 3 but AF is delayed. I don't start AF until the day I start my new pack of pills. After 3 months on Yaz, my periods ARE lighter and shorter .... although the first 3 months I had horrible cramping and extremely heavy periods on Yaz. In a nutshell, my PMS symptoms are pretty bad on Yaz and they last longer than on Yasmin b/c of the 24 day pack of pills.