Matt,
I'm not guessing, my statement has been proven on more than one occasion. The 370's have been put up againts DD3's back to back on the dyno. The DD3's actually produce a few less HP (5-10) than the 370's.
Heck, I bet if you were to call Diesel Dynamics they would tell you their DD3's are the same power level as 370's. It is not a secret.
I see you are a newer member. Back when 370's and DD3's were first popular the issues of what produces more HP had been hashed out several times. You do not see much about them anymore because there are several other injector offerings nowdays. I bet if you took the time to do a search you would find out that what I am saying is accurate.