For W2, the employer pays 7.65% and the employee 7.65%.

For self employed, they lump both portions onto you as “self employment tax” of 15.3%. However when you pay yourself a “reasonable salary” of only a portion and take the rest as ownership distributions you pay the 15.3% only on the salary. Salary may only be like 20-40% depending how aggressive your accountant wants you to be. (20-40% of 15.3% is going to be 3-6%ish which makes this compare favorably against 15.3 but also 7.65)

*I’m not an accountant. Just a guy who does this and is parroting what I’ve understood from my own accountant