I have a 90g SPS reef and have been dosing BulkReefSupply 2-part + magnesium. I got some B-Ionic as part of a tank teardown I bought, and I definitely think their alkalinity supplement (Part 1) is more effective than the bulkreefsupply stuff.
With BRS, I test my water, dose as needed, then retest, only to learn that I need to dose more.
With B-Ionic, I test my water, dose as needed, then retest, and the level is right where the calculators say it should be. I don't know what causes this, but it's always the case for me.
That being said, when my BRS additives run out, I'm going to buy more of it. It's well worth the trouble for the bargain it provides versus the store-bought stuff like B-Ionic.
Just my $0.02 (funnier comments this time, please)
-Dustin