Originally Posted by Mr.Domains

That is a slightly "uneducated" question... It's like saying "What gas do you prefer in you car, diesel or unleaded?" - it depends what your car is supposed to run on!

Different formats are for different types of image. I mean a logo with hard edges and flat blocks of color would look crap as a JPEG, as be 3 times the size as it would be as a 16 color GIF, whereas a digital photo saved as a compressed GIF looks like someone drew it in Paint on a Windows 3.x machine! There are different format for different purposed, spend a bit of time learning and playing with the different formats, and you will soon know what to use where.