I've heard the same thing about the yellow ones, but since there are so many yellow hybrids, some might be better than others. So basically if you see any yellow in bloom that you like, just grab it!
Of all the ones I bought earlier this year, the yellow had the shortest bloom period being barely one month versus over two months (my white one).
It is out of bloom now, but throwing lots and lots of new growths even in this hot weather here.
So I guess my yellow one is quite strong variety.