The main upside of running your own SD is that you can completely automate it, but I'm not sure how useful that really is.
No, the main upside of running your own SD web UI is that you can select and deploy your own checkpoints (not just using the base SD models), LoRas, embeddings, upscaling models, and UI plugins supporting additional services/models/features like multidiffusion (bigger gens and controls of which areas within the image different prompts apply to), ControlNet and associated models, video synthesis, combinatorial prompts, prompt shifting during generation to do blending effects, and, well, a million other things.
Also, you can completely automate it.
It's a little inconvenient to use non-base models and plugins this way (you pay extra for more storage), but it's definitely an easy way to use the full power of SD.
https://www.runpod.io/console/templates
Look for "RunPod Stable Diffusion". I spent a whole $0.35/hr playing around with my own SD instance that I had running in minutes.