Is tea tree oil or witch hazel more effective for getting rid of zits?

Neither works well. Both will disappoint you. This is the 21st century, you've worked hard, and you have a right to someting effective. I start with topical Clindamycin with or without a retinoic acid derivative. If this isn't enough, add oral Erythromycin or tetracycline as appropriate for the person. Dermatologists have even stronger stuff. Good luck.