Whats the BEST lighting is not really a question easily answered as it can be rather opinion based. Seeing as most of it is hear say,many people dont have experience in multiple fixtures.There really is no wrong way as long as the PAR reading are there and it leads to happy corals.I run all types of bulbs over my reef tanks from T-12s,T-5HO,Halide moguls & HQI, Power Compacts,and a number of LED units including marineland,Kessel,Evergrow,Reefstar, and DIY. All of them are growing many corals rather well. I can say you cannot get the same punch or visual effect from all of the lights but each one serves its purpose.For instance I have 1 metal halide mogul 250 watt over a 40 breeder and it is stacked with corals SPS,LPS,and then some but if I put a evergrow or the standard 55 3 watt cree LED fixture you need 2 to cover the area.If you do the math the LEDs are actual taking more power.Also on bulb exchanges it depends on the degredation of the bulb.Many of my T-5s and Halide moguls have retained there PAR ratings even after a year.I also dont find the bulbs to be too costly seeing as they cost from $11-$20 either T-5 HO or 250 watt halide"HQI is another story".Also if the depth of the tank is shallow I have some tanks with a shop light and good bulbs that rock some mad corals.You could argue heat into the equation but once again that is relevant to the setup and if it does not have sufficient heat exchange or if you live some where that the heat is negligible like me. So many pros and cons.
My point being BEST is a term hard to place on a light.Now as far as aesthetics its hard to beat a 2 channel LED that has UV lightin with its 460 Nanometer blue lights.I have boughten corals I already had because under the super UV actinic it looked UNREAL.I agree with wake that a metal halide is hard to beat as far as naturaly sureal looking goes...but they are now making LEDs to replicate the look of a halide.Sorry for the long post its just a hard question to answer.