Usually everything from Irodori's site will eventually come to fakku. The other way around has happened though, there have been some doujins published by Irodori that are in Fakku's site but have NOT BEEN AVAILABLE in Irodori's own website such as
Hypnotic Sexual Counselling: Compilation 1 and
Dick Note: The Hypnotic Sexual Guidance Register - Saki Touma's Record
So you should be fine with buying doujins on Fakku as long you have the patience, otherwise buy from Irodori's site for earlier access.