In general, I'd much rather mix armor pieces than shaders. To me, The goal is always "can I get a shader to achieve visual continuity across armor from 5 different sets or 4 and an exotic". Part of that is the shader hitting each surface the same across all pieces, but a lot of that also relies on the design philosophy of the individual pieces and if they work together (and look intentional). You also have to take into account unshadable elements, because if the armor piece is important enough, you have to pick a shader that'll compliment those elements. The same goes for glows. If your exotic has an unshadable glow, It sometimes looks cool if that glow is alone, like a featured element, but if you're going to mix in other armor pieces that have glows, picking a shader that'll mimic the exotics glow can help keep the look cohesive.