http://dictionary.reference.com/browse/equal
When one tank is superior to the other they are not equal. When one boltgun is superior to the other they are not equal.
Aside from the fluff specifically stating that their power armour provides "the same degree of armoured protection" - though people have tried to pick this apart and twist its meaning, too. And no, a difference of 2 points is not "the same degree", else we could just as well claim that Guard Flak provides the same degree of protection as Carapace. Seriously, how ridiculous does this have to get?
Instead of trying to negate quite crystal-clear official statements, how about bringing forth some quotes and citations yourself? Outside of this RPG, what led you to believe Astartes bolters are superior in the first place? Or, better yet, what led you to believe that there are two kinds of boltguns at all?

. I used to love Squats, I thought they were awesome (and I still have them show up now and again in my games), but GW apparently thought they sucked. 