Being just an amateur, I shoot everything 'wide' as I wear my glasses while shooting. That then gives me all the latitude I need to crop the images to whatever print-size I wish. I actually create multiple sub-folders in my 'finished' folder of: as shot, cropped 4x6, cropped 5x7, cropped 8x10. I also create a 'low-res for emailing' folder as well. Other than the as-shot folder, not all pictures will be in every folder, primarily because I don't think they are 'worth it'.
What that does is to give my 'client' (I work for free) a choice of what size they may want to print the photos as. But it gives ME the choice of what is and is not in each photo. Obviously, images cropped for 5x7 will usually have more 'objects' in the image than 4x6, be it background 'stuff' or perhaps someone in the background or off to one side making a funny face. I also print the 'better' images on my own photo quality printer and give them to the 'clients' as well, albeit a non-professional Epson that uses water-based ink.
I think I'm 'covered' for just about any situation. If they like what I printed, they'll likely frame one or two and lose the rest. If they really want to print their own at the cropped sizes or larger, they have all they need to choose from...or, at least tell their 'print shop' people what to print.