This research presents a design of experiments for early detection of bearing defects. Two measurement techniques (vibration and acoustic emission) are compared by using the ANOVA analysis. The results show the relationship between some time indicators to the degradation stage of bearing. The experimental design was considering the influence of the shaft speed, load and defect size as independent variables while the dependent variables brought on different time indicators. The objective of this study is to compare the effectiveness, consistency and reliability for bearing defect monitoring by using vibration and acoustic emission measurements. The results lead us to favor the application of vibration because it adapts better to the vast majority of situations, while the acoustic emission allows for the reliable detection of the fault but not for accurate tracking. In fact, acoustic emission is recommend in the case of low speeds less than 400 rev/min. A new indicator called TALAF is most relevant for monitoring the defect size with a contribution of 97.87% in vibration and only of 76.35% by acoustic emission. Finally, the effects of shaft speed and the radial load increases with the defect size.