There are some restaurants that are exclusive on certain platforms (UberEats for example is exclusive with McDonalds), so if you want that, there's only one game in town, but most people I know who use these platforms regularly (myself included) aren't using them for a specific restaurant. It's more like, "I want sushi! I wonder what is available on my platform of choice?"

Beyond they all have slightly different pricing models, but at the end of the day they all cost about the same.