I'm not sure how angles affect efficiency, when it concerns lighting. But, given the lighting equipment/sources that you mentioned, the light would have a greater chance of hitting the exposed coral at a perpendicular angle. If the angle increases efficiency of uptake, then both linear and point source (with or without good reflectors) lighting would benefit from mounting the corals with more exposed tissue. This is HIGHLY speculative; it's just my opinion and thoughts. I could be off base.
From personal experience, I have noted this in my old 65g: Two Millepora frags from the same colony (I bought 2 in case one died...I liked it that much) were placed in my 65 in close proximity. They both had flow coming from separate MP40s, set at 100% on Reef Crest. They both were positioned almost the same distance from one of my 250w Phoenix MH. The only difference was how they were mounted; one was mounting vertically (still leaning at an angle), the other horizontally glued.
The horizontal one grew slowly, only spreading a base for the first few months, while the vertical one grew new branches. During the next few months, around a dozen tips sprouted on the large base of the horizontal frag, while the other continued the grow longer. 9 months from buying them, the horizontal was a nice mini-colony, while the vertical was half the size, by comparison.
This is a year: you can see them both on the left and right side of the Cali tort. The long breaches on the smaller coral were the new growth.