the Soyuz is old and pretty reliable, while the upper stage that failed in the VS09 flight of the "Soyuz at Guiana" (https://en.wikipedia.org/wiki/Soyuz_at_the_Guiana_Space_Cent...) program - Fregat - is relatively recent development - 199x and its version is what also failed the recent Russian mission to Mars - https://en.wikipedia.org/wiki/Fobos-Grunt