Magnetic tunnel junction (MTJ) has been successfully used in spintronic devices, such as magnetoresistive random access memory, tunneling magnetoresistance (TMR) sensor, magnetic logic. In the TMR sensor a special magnetic structure is used between the free layer and the pinned layer of an MTJ to realize a linear output. So far, five types of TMR linear sensing units (TMR-LSNs) have been developed based on MgO MTJs, which are artificial-indirect-double-exchange-coupling-, magnetic-field-biased-, in-plane-, perpendicular-, and superparamagnetic-TMR-LSN, respectively. In this paper, the five types of TMR-LSNs are combed and their magnetic sensing performances are systematically compared with each other. First, the five types of TMR-LSNs each have a linear resistance response to the external magnetic field with a changeable sensitivity, a linear field range and a low frequency noise level. Second, in the five types of TMR-LSNs different magnetic structures are used to realize the same aim that is to obtain the optimized performance parameters, which is of significance for putting TMR sensors into practical applications. Third, the five types of TMR-LSNs are suitable for different application scenarios due to their respective performance parameters. Therefore, we believe that our summarized discussion in this paper will help people to explore and find the relevant applications of TMR sensors based on the five types of TMR-LSNs.