I have worked with CreateSpace before and used AI vector images on the cover and interior PDF of a book, but the images all printed pixelated. After complaining, CreateSpace told me to only use 300 dpi TIFFs since vectors were over 450 dpi. So, I used Photoshop to create 300 dpi images, plopped them in my files, and, lo and behold, the next print run was perfect. The 300 dpi TIFFs were much clearer than the vectors.
Around the web, however, everyone seems to say to use vectors for print. Is this valid? Is CreateSpace just a low-quality printer whose submission guidelines I should ignore for other print work? It's very confusing. I would appreciate any input you might have. Thanks :)