During penetrative intercourse I don't want to delay my orgasm, it is very intense as is and takes time to acheive so once it comes I grasp hard onto it and let it take over.
During masturbation I delay especially while watching porn. I like to synchronize my orgasms with the scene I am watching so that I orgasm at the same time as a girl squirts or at the same time a girl "orgasms". The orgasms I get during solo are not as powerful as the ones I get during intercourse so delaying helps to amp them up a bit.
For my partner I only delay his orgasms very rarely. I have done it a few times but it is such torture to him that I avoid delaying his orgasm more than once. I ususally only do this during oral sex. It does make his orgasm more pleasurable.