It depends on the types of LPS you intend to keep. I personally have (2) 250Watt 14K (PlusRite) MH SE over my 90 gallon (4'Lx18"Wx24"T). I have a Torch, Frogspawn, Hammers, Candy Canes and an Alveopora in the middle to upper area, then an Acan, a Favia and a Fungia all on the sand.
I've only used MH, so I can't say much for LED and T5.