What are the key differences between the Canon 18-135 USM and STM lenses, and which one would be a better choice for my photography needs?

The key differences between the Canon 18-135 USM and STM lenses are in their autofocus systems. The USM (Ultrasonic Motor) provides faster and quieter autofocus, while the STM (Stepping Motor) offers smoother and more silent focusing, especially during video recording.

If you prioritize fast and accurate autofocus for still Photography, the USM lens would be a better choice. However, if you focus more on video recording and want quieter and smoother autofocus, the STM lens would be more suitable for your photography needs.