Properly done (sqrt(2)/2 half steps), half stepping gives the same static torque as full step, and higher acceleration without skipping steps, so more effective torque with varying speed.

Properly done (sqrt(2)/2 driven half steps), half stepping gives the same static torque as full step, and slightly higher acceleration without skipping steps, so more effective torque with varying speed. Going all the way to micro-stepping increases the acceleration slightly more. Using 0.5 driven half steps results in less torque.