Quick Claw is not a good item for competitive at all. It works randomly (and rarely, only 20% of the time) and there's no guarantee it will activate on a turn where you actually did go second.
You can't base your decision-making on low % random chances, so Quick Claw plainly doesn't factor into your game most of the time.
In other words, you are never going to make a play that depends on Quick Claw working. On the other hand, you can always trust an item like Choice Scarf to hit a speed benchmark or Life Orb to secure an OHKO. You want items with a consistent, dependable and useful effect. Quick Claw is an unpredictable luck item.