Chapter 8 - Rotational Motion and Equilibrium - Learning Path Questions and Exercises - Multiple Choice Questions - Page 301: 12

(a) the sphere reaches the bottom first.

Moment of inertia of solid sphere = $\frac{2MR^{2}}{5}$ is less than that of annular cylinder = $\frac{M(2R)^{2}}{2}$ of radius 2R. More the moment of inertia, more the resistance to rotation, the cylinder will rotate slowly compared to the solid sphere. So, the sphere reaches the bottom first.