Not quite the same flow.
My 1st Song is written in 6 / 8 time, so basically there are six beats per bar.
Spaceship is written in 3 / 4 time, so basically there are three beats per bar.
Although the two songs have a slighter similar feel, they are quite different. In essence, Kanye's flow in Spaceship has an emphasis on the 1st beat of the bar and Jay-Z's flow has an emphasis on the 1st and 4th beats in the bar.
Here are 8-bar lyrical examples that showcase the difference between the songs:
My 1st Song
Y'all wanna know why he don't stop /
Y'all wanna know why he don't flop /
Let me tell you people why /
Came from the bottom of the block I
Spaceship
If my manager /
Insults me again /
I will be /
assaulting him
Overall, My 1st Song is actually a bit more complex because Jay-Z's flow actually alternates between 3 / 4 time and 6 / 8 time and uses pauses for emphasis, which complicates rhythm counting.
For example, the lines "When I was born <silence> It was sworn <silence> / I was never gon' be shit" are complex to count because the 4th beat, which is normally an emphasis beat, is silent. And in the second line he emphasis all three words (gon', be, shit) which temporarily switches the feel from 6 / 8 to 3 / 4 in same way that Kanye emphasizes the three beats in "assaul ting him".[list type=decimal]
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