In my book consistency is king: so if you hate endurance rides and find easy SS rides on the trainer more engaging, stick to sweet spot. If you find that all that intensity is tiring you out and you want something mellower, an endurance ride sounds like the right way to go.
If you are ok with either, I’d probably err towards going for an endurance ride as that will broaden your base. The amount of work you do on the Sunday sweet spot rides is usually quite small in comparison, so it doesn’t push the needle too much. More endurance will improve recovery and repeatability, i. e. it will increase the length of your life bar while not touching the power bar.