Fair point, although you cant refute the fact that hills are not better for strength development than strength training? Also specificity of training is fundamental to performance. Yes running hills means you can hit a high HR without as much speed as a flat run, but why is this better than running flatter at a faster speed? The biomechanics of running up a hill are very different to running flat therefore when working on aerobic capacity this comparison could cause greater fatigue in the muscles and reduce the volume of training you can do at this intensity (i.e. you are fatiguing yourself peripherally e.g. at the muscles, when in fact the target of aerobic training is to fatigue centrally e.g. the cardiorespiratory system)I don't think something can be deemed as less effective at improving aerobic capacity because it's something you don't do a great deal in races? Running hills gets the cardio system, as well as leg muscles, working overtime! I know I can certainly hit higher heart rates 'more easily' by running hills than on intervals. Seb Coe ran a LOT of hill intervals - yet I can't remember seeing him run up any hills on the track
In my opinion, intervals for specifically working on improving speed, hills for improving strength and overall fitness. The two combined will be a great addition to your training schedule to work towards you main of becoming a better runner.
CorrectGenerally though, if someone improves their leg strength, chances are their speed will also improve If I ever get to a standard that requires it, I'll be sure to read up on the subject further :d