I don't "prefer" it over oranges (blood orange is probably my favorite fruit), but I certainly consider it to be worthy of consideration...

I love a grapefruit for breakfast... the GF an I will split one every once in a while... if it's not sweet enough, I'll sprinkle some sugar (for her) or stevia (for me) on it to cut the sourness. Makes an excellent lo-cal brekkie.

Grapefruit also have some interesting properties that other citrus do not possess. For example, there is an enzyme that is unique to grapefruit, that blocks fat absorption in humans. So if you eat a grapefruit, or have a glass of grapefruit juice, before chowing down on a big sausage/bacon/potatos/eggs/etc. breakfast, you will actually "pass" more of the fat than you otherwise would.

There is another enzyme, also unique to grapefruit, that magnifies the effects of certain types of drugs. (It's why some drugs carry warning labels against grapefruit eating). You can google this for more info.