I use CaribSea ARM. Effluent drips into sump section where my skimmer is located. My skimmer air intake is routed to pull air from outside.
The effluent ph will ultimately be dictated by how you run the calcium reactor. I believe the arm media claims to dissolve at higher ph than others, but you can adjust to what suits your setup.
For what it's worth, I like the arm media. I can't give an objective opinion on others, but that's because it has been great for me so I haven't tried anything else.
My opinion, if the setup has adequate aeration, through surface turbulence, skimmer, or whatever, and you put at least a little thought into effluent placement, the pH issue should be no concern at all.
