The right accommodation depends on three things: where you want to spend most of your time, how large the group is, and how much logistics you want to manage.
For nightlife-focused weekends, staying in the Gaslamp Quarter means walking to every major venue — no transportation costs, no coordinating Ubers at 2am. For groups that want beach time as the centerpiece, Pacific Beach offers boardwalk access and a more laid-back atmosphere, at generally lower rates.
Groups of 8 or more should seriously consider a large vacation rental over multiple hotel rooms. The per-person cost is usually lower, you get shared common space, and the group stays together instead of spreading across different floors of a hotel.