Spin transfer torque magnetoresistive random access memory (STT-MRAM) technology has been gaining interest as an alternative to SRAM as it possesses unique properties such as nonvolatility, higher density, and good scalability. Magnetic tunnel junctions (MTJs) based on shape anisotropy, interface anisotropy and crystal anisotropy have been demonstrated with the common goal of reducing the switching current while maintaining sufficient nonvolatility. However, the research community has yet to reach a strong consensus on which MTJ technology will prevail in deeply scaled technology nodes such as 8nm. To answer this open ended question, this paper presents a comprehensive study on the scalability of STT-MRAM based on various MTJ technologies: namely, in-plane MTJ (IMTJ), crystal perpendicular MTJ (c-PMTJ), and interface perpendicular MTJ (i-PMTJ). For a practical analysis, our simulation model captures key physics of STT switching in various MTJs by incorporating dimension-dependent effective anisotropy field (HKeff) into the Landau-Lifshitz-Gilbert (LLG) equation and considering realistic material parameters.