Not quite sure about that. With HPS you get a strong concentration of Orange/Red light, and very high lux. With LED, the spectrum is broader (so you SEE less of it), lux is much lower (lux is measure of intensity of visible light, not accounting for other spectrums), but PAR is much much higher.
Not saying you should´t angle! I plan to do it myself. All I am arguing is that only because you SEE more reflection on the mylar with HPS does not mean there is less reflection using LED.
Of course, if the main cola jumps out and you measure the light from its top, then yeah, the lower buds get less light. But that is also true with HID's. So angling down is def a great idea.