We evaluated the effect of conventional and corrective image reconstruction methods on reduced acquisition time for detecting a myocardial perfusion (MP) defect in MP SPECT using the Channelized Hotelling Observer (CHO). Using the 4D Extended Cardiac-Torso (XCAT) phantom, we simulated realistic transmural and endocardial MP defects in various location and size. Realistic Tc-99m Sestamibi MP projection data were generated using an analytical projector that included the effects of attenuation (A), collimator-detector response (D) and scatter (S) for various count levels simulating different acquisition times. They were reconstructed using the 3D FBP without correction and a 3D OS-EM method with ADS correction followed by a smoothing filter with various cut-off frequencies. The CHO followed by receiver operating characteristics (ROC) methodology was applied to the reconstructed images to evaluate the detectability of a MP defect in each method for different defect anatomies and count levels. Areas under the ROC curve (AUC) were computed to assess the changes in the MP defect detection. The results showed that the 3D OS-EM with ADS corrections showed significantly less changes in AUC value and gave overall higher AUC values than FBP at all cut-off frequencies of the post smoothing filter, count levels and MP defect sizes. The difference in AUC increased towards less smoothed images where the 3D OS-EM with correction was able to provide similar AUC values with 20-40% reduction in acquisition time compared to FBP. The AUC values for smaller MP defects were lower for both reconstruction methods with smaller differences. We concluded that the 3D OS-EM with ADS corrections provides higher performance in the MP defect detection task. It allows increased reduction of acquisition time without loss of MP defect detection in MP SPECT compared to the conventional FBP method especially towards less smoothed images.