Mandriva is less frequently released and like suse fills in gaps with their own technology such as system control centre. They have also been very bad at creating a community which leads to forks like PCLinuxOS and Mangia
I don't quite understand what you mean by "fills in gaps". There are no gaps, YaST on openSUSE is provided in addition to pretty much what anyone would expect on any distro.
Edit: I see what you meant in a comment later/earlier in this thread.
