Speaking as a writer...it depends if you have an ego. If you're not overparticular about having your name on the spine, getting $50,000 for writing a book for the Ludlum/Andrews/Patterson brands beats getting $5,000 for a MMP original thriller, and both take around the same amount of time--in fact, the brand-name is probably easier as the setup is done for you. Art is a wonderful thing, but we've all got bills to pay.
Or you could do both--one for your own satisfaction and one for your bank account.
As a reader, if it's a good story, does it matter who wrote it? (I wouldn't call V.C. Andrews stories, whether written by the late authoress or her ghostwriters, good, but tastes differ. I thought Flowers in the Attic was fabulous when I was 13.)