The RX 550 without any doubt. The GT 1030 is just an entry-level GPU, not meant for heavy gaming loads. Any GTX----Model is better >>>>>> GT-----Model.
The GT 1030 card seems ideal for e-sports gaming, HTPC enthusiasts , or replacing integrated graphics in home theater PCs or productivity machines, especially given its multi-monitor support. As it's not a GTX card, it lacks support for premium GeForce features like G-Sync, Ansel, and GameStream, though it does play nice with the GeForce Experience app.