I certainly see what you are saying and agree but "better" is subjective in this case.
If we are saying better for corals then of course all we want is that they get enough light to grow which can certainly be provided by each of the above mentioned. But if what we are talking about is better for a given situation then we can argue that some lights are better than others.
For example T5 vs MH or LED for depth. T5 does will not penetrate as deeply. Growing corals low or on the sand bed will be difficult to do well in a deep tank with T5's.
If heat is an issue then LED comes out on top, same when dealing with electricity costs and bulb replacement costs. I'm a fan of LED because I feel they are better for most situations that arise.
Water quality and flow are huge factors and cannot be ignored. Really if you do poorly on any of the three, light, flow, or water quality, corals will not thrive.