I think Diamond is better in one way, it may seem like a small thing, but it's important to me: (Minor Spoilers!)
In Hakutai Forest and Hakutai mansion (Cut required), Pearl has Ghastly and Misdrevus to pick from, obviously Ghastly is the better choice.
Diamond has Ghastly and Murkrow to catch, which can be on the same team without one overshadowing the other.
My point is that Pearl has two overlapping pokemon where Diamond has two non-overlapping ones. Don't forget that Mafia bird = win.
Other than that there really is no difference between the two. Post-game stuff like T-tar and Mence can be obtained through trades with little trouble.
In Hakutai Forest and Hakutai mansion (Cut required), Pearl has Ghastly and Misdrevus to pick from, obviously Ghastly is the better choice.
Diamond has Ghastly and Murkrow to catch, which can be on the same team without one overshadowing the other.
My point is that Pearl has two overlapping pokemon where Diamond has two non-overlapping ones. Don't forget that Mafia bird = win.
Other than that there really is no difference between the two. Post-game stuff like T-tar and Mence can be obtained through trades with little trouble.




