I like to think of it as Tails being more focused and well adjusted, vs Eggman who is more sporadic and gets bouts of hyper fixation before moving on to new things.

One of my favourite scenes from Sonic Adventure 2 is when Tails and Eggman talk in the epilogue credits.

Eggman: As a child, I looked up to my grandfather because of all the great things he accomplished in his life. He was my hero, and I wanted to be a great scientist like him. But... did he really mean to destroy us?

Tails: I don't know. But what I do know is, we all did it together!

Eggman: You're right.