I would guess the rearrangement is due to the writing in the second cover.
In the first cover the large title text can be seen through because it has gaps between the letters. That means Piccolo's clothing can be seen behind the letters. In the second cover the writing "DRAGON BALL" has no spaces between it, so if Piccolo had to be moved further down to make his body viewable.
In the first cover there's writing in the middle (between Goku and Piccolo's heads), but because Piccolo is moved down there's no room there for writing. They wanted to write the pink kanji, 8, the purple hiragana and the orange-red kanji (let's call it "SPECIAL TEXT"), but since there was no room in the centre they redrawn the characters in a new arrangement to create space on the left, just under the "DRAGON BALL" title.
Or maybe the part about Piccolo's body is irrelevant and they were willing to keep Piccolo's body behind the title, but they just felt that the central space seen in the first cover isn't enough for the SPECIAL TEXT, so they redrew it all. Or because the text says something that makes more sense to have in the top-left than in the middle of the page.
Whatever it exactly was, I think it's due to trying to accommodate that SPECIAL TEXT.
However it is still peculiar that they've redrawn it with Shen and Mercenary Tao swapped, since it makes more sense to group Shen with Piccolo and Tao with Tien.
