This paper compares digital and analog transmission schemes for wireless federated learning (FL) in resource-constrained networks. It introduces a unified framework to evaluate the performance of both schemes under imbalanced device sampling, strict latency targets, and transmit power constraints. The key findings include: 1. **Digital Transmission**: Decouples communication and computation, making it challenging to support uplink transmission from devices with limited bandwidth. Performance is primarily limited by communication. 2. **Analog Transmission**: Allows over-the-air computation (AirComp) and achieves better spectrum utilization but reduces power efficiency and is sensitive to computation errors due to imperfect channel state information (CSI). 3. **Optimization**: Device sampling optimization is crucial for both schemes, with digital transmission benefiting from better power utilization and analog transmission from spectrum efficiency. 4. **Convergence Analysis**: Analytical results show that digital transmission is less efficient with limited resources, while analog transmission gains in terms of optimality gap with increasing device number but is sensitive to CSI imperfections. 5. **Impact of Parameters**: The number of quantization bits and CSI accuracy affect performance, with optimal settings varying between the two schemes. The paper provides a comprehensive comparison and offers insights into the deployment and design of wireless FL in resource-constrained environments.This paper compares digital and analog transmission schemes for wireless federated learning (FL) in resource-constrained networks. It introduces a unified framework to evaluate the performance of both schemes under imbalanced device sampling, strict latency targets, and transmit power constraints. The key findings include: 1. **Digital Transmission**: Decouples communication and computation, making it challenging to support uplink transmission from devices with limited bandwidth. Performance is primarily limited by communication. 2. **Analog Transmission**: Allows over-the-air computation (AirComp) and achieves better spectrum utilization but reduces power efficiency and is sensitive to computation errors due to imperfect channel state information (CSI). 3. **Optimization**: Device sampling optimization is crucial for both schemes, with digital transmission benefiting from better power utilization and analog transmission from spectrum efficiency. 4. **Convergence Analysis**: Analytical results show that digital transmission is less efficient with limited resources, while analog transmission gains in terms of optimality gap with increasing device number but is sensitive to CSI imperfections. 5. **Impact of Parameters**: The number of quantization bits and CSI accuracy affect performance, with optimal settings varying between the two schemes. The paper provides a comprehensive comparison and offers insights into the deployment and design of wireless FL in resource-constrained environments.