It'll still be an imperfect test--iPhone 5 versus iPhone 6, which means different cameras. Isn't the 6 camera basically the same as the 5s according to the teardowns? Unfortunately, I don't have a 5s to try.
Noticed out something else last night though in informal testing; the 6 seems to blow out highlights when set to the same ISO/shutter speed as the 5 that's still on 7.1.2. Since being able to do most manual adjustments came with iOS 8, I used Pure Shot on both cams, let the 5/7.1.2 pick it's own settings, then matched those in full manual mode on the 6. Result was the 6 image was noticeably brighter overall, all whites in the image blown out. And yes, the Monet effect didn't seem present on the 5, though it was a low light ISO 800 crappy handheld shot. Plenty of noise, of course, but details were present and less smoothed.
Need to wait for a dry day, since I'll do this outside during daylight. But if I can manage it this week, I'll post it. It should be interesting, anyway, even if it's not perfectly matched because it's with a 5 instead of a 5s.
I think the purpose of the testing is mainly to find out how far backwards the iPhone 6 has gone in terms of camera performance right? So it shouldn't really matter if the cameras between each phone are different as we want to find which one is best?
Also I always had a sneaky suspicion that the 6 had less dynamic range than the 5/5s but wasn't completely sure so it's reassuring you've noticed it as well (even if the overall image is brighter)