Clearly the Pacific War would have been more humane. There still would have been racism at play among the white Allied powers, but if the Japanese behaved honorably, obvious Japanese military capabilities would have overcome some of that, and the Japanese would be respected. The Allies might well have been less insistent on unconditional victory over a Japan that was less fanatic.
The difference would really take effect during and after the end of the war. A less fanatic Japan might well have seen the writing on the wall as early as 1943 and sent out serious peace feelers that the Allies might not reject out of hand. The war might have even ended a year earlier in an armistice with Japan retreating to its pre-1937 gains, with the ultimate situation in China to be resolved in an eventual peace treaty once the other Axis powers were defeated. There would be no push for war crimes trials, Japan would possibly not be occupied. Japan might be treated more like Italy was OTL...a basically reasonable and former 1914-1918 Ally that just went a bit crazy in the 1930's.