What is the difference between Tc-99m sestamibi and Tl-201?

Tl-201 redistributes; therefore, only one injection is necessary.
Tc-99m sestamibi does not redistribute; therefore, a second injection is required for rest images. Its longer half-life allows images to be obtained much later.
Tc-99m sestamibi has less attenuation than Tl-201 owing to the higher energy of technetium