Until a week ago, I would have said your 36mm Challenge tires. ‘been playing with some 32mm GP5000s tubless. Half the rolling resistance of the Challenge tires is kinda tempting. For me, it would be whether I felt more beat up, or if I was wondering if my legs would give out.
Granted, there is not a huge difference between 25mm 4000s and 32mm TL 5000s. The 4000s have 50% more rolling resistance (but still, that is only 10 watts/pair) and are 5mm narrower (28 vs 33mm), and need about 25% more pressure. For that type of riding I go for 32mm slicks.
What the heck – go for the cumfy big challenge tires (unless you are really in a hurry).
(On the other hand – the standard BF answer is always: buy new tires).