This is going to sound like nit-picking, but do you mean pH, or specific gravity? By the context of your question, it seems that you mean specific gravity...
Some suggest that, in a fish only tank, using a slightly "light" mixture provides a better environment; the rationale being that freshwater holds more oxygen, so any move in that direction makes respiration easier for the fish.
I'm not so sure about that, but if you're not planning on doing any breeding, and intend to stick with a FO tank, then matching water with your LFS would certainly make acclimatization easier on new fish.
Many LFS keep their salinities low to help control parasites. Marine parasites are easily killed by low salinities, and it can be used to treat fish prone to ich. In the home aquarium, quarantine of the fish prior to introduction, and treatment is needed, is a much better option. The fish can tolerate the lower sg for a while, but IMO, it may cause problems in the long run. Corals and inverts require the higher sg--they can't tolerate the low levels like fish can.