Regardless of use, 5w40 is better than 10w40. Both are same viscosity when hot, but 5w will circulate quicker when cold. (Both are significantly thinner when hot than 5w cold, so if anybody comes along and says 5w is 'too thin' that is total nonsense!)
This is scientific fact not opinion, just saying that because lots of folk think the old wives tales they've heard down the pub are gospel...
Plus 5w40 is usually fully synthetic, 10w40 is usually semi synthetic. Fully is better than semi, again, some people think some engines 'need' semi, which, again, is nonsense.