Cellular base stations rely on proprietary downlink scheduling algorithms that vendors independently develop to fairly and efficiently schedules traffic to competing users. Schedulers from different vendors can make different scheduling decisions depending on channel conditions, buffer status, fairness, and capability. This work is the first to show the significant scheduling policy differences in a head-to-head comparison of the behavior of downlink schedulers across four base station vendors (Ericsson, Samsung, Nokia and Huawei) running on four cellular providers (AT&T, Verizon, T-Mobile and Vodafone). The evaluation is based on 500Gbytes of downlink transfers across 20 base stations in five cities during semi-controlled network and signal conditions. In particular, we observe different strategies for allocating radio resources, for rate control, and for handling users with asymmetric channel quality. These results challenge the assumptions made about downlink scheduler uniformity in prior cellular performance measurement studies.