Access Devices (1AD) for crossbar resistive (1R) memories are compared via circuit-level analysis. We show that in addition to intrinsic properties, AD suitability for 1AD+1R memories is strongly dependent upon (a) nonvolatile memory (NVM) and (b) circuit parameters. We find that (1) building large arrays (≥1Mb) with ≥10uA NVM current would require MIEC ADs and moderate NVM switching voltage (≤1.2V). (2) For all ADs high NVM voltages (>2V) are supported only at sub-5uA currents. AD improvements to expand this design space are discussed.