I do a similar distance once or twice a week, and have the luxury of choosing a road or off roadish route – around 200-250M of climbing each way.
Road bike is quickest and best option for me – I get back in time to see my children, and it doesn’t take much longer than driving. Still a good workout. Best all round option I think.
MTB is fun on a sunny day with a diversion on the way home.
I like riding SS but commuting on it wasn’t happening – the hills are too steep (1/5 on the way home in places) for a good ratio to get the speed up on the flat bits. I take the mtb ss if I know I don’t have to rush, as there’s an offroad return leg that isn’t so steep.