You can save stuff like that for what the differences are, but if you look at the bigger picture, DBZ and One Piece have a lot more in common with each other than say, FMA and K-on.
If two shows are in the same genre, it makes a lot more even ground to compare and contrast than two shows that have absolutely nothing to do with each other. With two action shows, you can compare and contrast how their plots are set up, how the action scenes play out. Maybe one is more plot focused and the other is character focused etc.
With two shows in completely different genres, there’s even less common ground to find, outside of “well they’re both anime... so.. yeah”. It wouldn’t be fair to say FMA is better than K-on because it has fight scenes when the latter has nothing to do with fighting. It is a lot more fair to say DBZ has better fight scenes than One Piece because [insert reasons].
You where in getting at here?