What is the significance of the Gita’s reference to Krishna as Bhagavan because Mahabharata also refers to Shiva as Bhagavan?

From: Narendra Bhati
I heard in one of the Lectures of Srila Prabhupada where he says that Krishna is Bhagwan thats why in the Bhagvad Gita Krishna is mentioned as “Shri Bhagwan Uvacha”.
Since Bhagvad Gita is a part of Mahabharat, when i read Mahabharat at many places Lord shiva was Mentioned as “Shri Bhagwan Uvach” and yet at many other places i read where Krishna is mentioned as “Shri Krishna/ Vasudev uvach”. Going by this explanation isnt Lord Shiva Bhagvan and isnt Lord Krishna less than Bhagwan.