The rise of renewable energy and electrification is exacerbating power grid congestion, and topology control is emerging as a promising approach to alleviate congestion. This study investigates the impact of graph representations on topology control. We identify problems with existing uniform graph representations and propose a heterogeneous graph representation that addresses these issues. We compare and evaluate GNNs using these two representations with a fully connected neural network (FCNN) in an imitation learning task. The results show that heterogeneous GNNs perform best in in-distribution network configurations, followed by FCNN and uniform GNNs. Furthermore, both GNN types generalize better than FCNN in out-of-distribution network configurations.