Bruce has an obviosly different personality.
Particularly in Avengers 1, where Bruce was the only person who saw through Natasha’s charade.
Compare that to Steve, who’s interestingly frustrated with Natasha’s secrecy in Winter Soldier. Bruce straight up never bought was Natasha tried to sell him. He knew she was an expert liar and he knew she was scared of him as Hulk.
Its a weird development that Natasha quicky stops being scared of Hulk. Despite not being a super spy, Bruce knew very well Natasha only pretends to hold all the cards, but since he’s very well aware he’s more powerful than her? He’s not afraid to call out her bullshit.
I really liked their dynamic. Different from Natasha’s other dynamics where she just rolls her eyes at the men and makes quips.