What are the key differences between the Canon 70-300 and 100-400 lenses, and which one would be a better choice for my photography needs?

The key differences between the Canon 70-300 and 100-400 lenses are their focal lengths and maximum apertures. The 70-300 lens has a shorter focal length range and a smaller maximum aperture compared to the 100-400 lens. The 100-400 lens offers a longer reach and a wider maximum aperture, making it better for capturing distant subjects and low-light conditions. If you need more versatility and reach in your Photography, the 100-400 lens would be a better choice.