I had Yaffe 14" on my 12 SERG and have them on my 13 SERK. My 15 SERGU I wanted the Yaffe but after 5 months of trying to get them I went with 14 Factory 47. My 17 SESG has Yaffe 14" on it.
My take on the two bars. First thing I noticed on the 15 when the Factory 47 were put on was they felt shorter. They were, as I measured both. 14" factory 47 were 12.5 from grip to bar clamp and the Yaffe were 14.5 measured the same way. The Factory 47 are wider than the Yaffe and the Factory 47 are thicker which in my opinion looks better. Grip angles are pretty similar, both are comfortable on 750 miles days.
Strange thing is my 14" Yaffe on my SESG feel taller than my 14 Yaffe on my SERK. Not sure if its due to how a bar is designed for the SESG or if the angle is different, will check today,
I have no problem with either bar, and like them both. The 17 got the Yaffe cause I could get them in black faster.