This paper presents a comprehensive benchmarking and co-optimization of 6T SRAM bitcells designed with 5nm vertical and lateral gate-all-around nanowire FET technology for the first time. A variety of 6T SRAM bitcells configurations combined with different device integration scenarios will be discussed. Our results show that an ultra-dense SRAM bitcell (0.01 um2) can be achieved with vertical FET architecture. The bitcell designed with vertical FET are preferably targeted for low power applications while the lateral FET-based SRAM bitcells could provide 4.5x higher in performance, but resulting in a penalty of 17x increasing in the leakage current compared to the vertical designs. A Vmin of 0.45 V could be obtained for 122 SRAM bitcells implemented with vertical devices.