Bluray < DVD version... content wise?

[Furious911]

Hey fellas, I have a massive collection of special edition DVDs that I want to replace with the Bluray counterpart and I'm gonna be selling them all here soon, my only question is do Blurays automatically come with all the extras and behind the scenes stuff that a full on special, say 3 disc edition DVD would have?

I love the extras so I'm having anxiety (not really but yeah) about switching them all out, for example I have a 3 Disc Directors Cut DVD set of Hellboy with a crapload of awesome extras, the Bluray looks to be 1 disc... does it have all that stuff on it?

I kinda figured that the Bluray versions always had the most extras and better content then DVDs would and now I'm thinking about it and I'm not so sure, can anyone shed some light on this for me?