The Canon EF 50mm f/1.4 is not a ring type USM, it is a Micro USM. A word of advice: buy a hood and also park the lens at infinity. If you don’t the front of the lens will protrude from the barrel. Any force on the front of the lens can bend the plastic focusing helical, causing the USM to fail.

The first symptom is a failure of the AF mode, eventually the lens will fail to focus manually, as well.

There are dozens of blogs and forum posts documenting this issue

Repair guide.

The Sigma 50mm f/1.4 is more expensive and heavier, but suffers from backfocus issues, especially wider than f/4.

The Canon 50mm f/1.8 is cheaper, but exhibits vignetting until f/4, has harsher bokeh and has AF issues in low-light.