Mainhand/Offhand too? And what about the set bonuses that come with the campaign armor only? Statistically the Black Hole gear is identical to Campaign, but you still aren't getting exactly the same gear.
Mainhands are the big undisputed reason. Offhands aren't simply because they vary class by class. For example the Black Hole Med Tech mainhand is better for DPS commandos than the Campaign Eliminator's offhand.
Similarly the set bonuses on armorings is a double edged sword. For me, I prefer the superior DPS armorings from various pieces of Black Hole gear in Rakata shells over putting the armorings from Campaign which are, in my case, 3/5 Endurance heavy tank armorings. The only piece of gear I can't get a 68 aim DPS armoring from BH is in the body slot, but campaign eliminator's body doesn't have that armoring either so my rakata armoring is better. The only Trooper body piece with a 68 aim armoring is the Combat Tech body and I'm not sure, but I think Campaign set bonuses trump shell set bonuses so my Rakata body armoring will always be better till I can unslotted armoring to put in it's place (which hey I DO need to do HM EC for).
Now that was all pretty DPS commando specific, but point is that it will vary from person to person.
This more or less just exposes problems in the campaign itemization though. In my opinion it should have been better than Black Hole, but there you are. In the meantime I'll continue doing HM EC just because my guild hasn't beaten it yet and I like the challenge.