What is the better buy: Canon EF 24-70mm f/2.8L USM or Canon EF 70-200mm f/4L IS USM lens? I'm stuck between the two because I want a lens that I'd versatile for being used on head shots, body shots, and then taking pictures of the Eiffel Tower in the morning and at night and then for the Vatican City and other amazing places in Europe. But which lens of these two is good? And if not which other lens is there out there by Canon that I can get that takes sharp pictures in low lighting and just flash as well that zooms far enough and takes wide angle pictures and/or landscape because I want to be able to take pictures but that can take either landscape type pictures and other things. So someone please help me here..