Use both, but live practice should become part of your preparation before the interview.

Solo drills are efficient for fixing specific skills such as math, structuring, or exhibit reading. Live cases add the interaction you cannot fully reproduce alone: listening, clarifying, speaking clearly, reacting to prompts, and handling interruptions.

You might use solo work to improve a weak math skill, then test that skill in a live case where you also have to explain the calculation and respond to the interviewer.

Keep solo drills for targeted improvement and schedule regular live cases to test the whole performance. As the interview gets closer, make the live cases increasingly realistic. For more practice guidance, see the Case Interview Guide.

Solo work helped my math, but live cases exposed how much I rambled when someone was actually waiting for an answer.