For info on the "grams" issue see Terry Love's site.
The Serif uses the Kohler Ingenium flush system ( combo rim flush and siphon jet). This system is a decent flusher.
Not familiar with the Pinoir.
If you do any research at all on flushing, you will see that Toto has sort of written the book on this, especially their G-max. Cimarron and Champion are the new kids on the block in this arena. I personally have a Sloan FLushmate in a Mansfield toilet ( had this for 12 years now.) We like this a lot and would not change. Power flush is noisy, and this is not acceptable to some people. Also, repair parts are more expensive. In the 12 years I have replaced the cartridge ($26) three times and the lower supply assy. ($55) once. All in all I am sold on power flush, but the performance of the Toto seems to equal my Flushmate.