I don't know, time travel just confuses me to bits. I always think about it too hard and it ends up ruining the plot completely.
PIT made me feel like I was stuck in the castle most of the game, I would've enjoyed it morw if you could go to both the past AND presnet areas such as toad town in the present and toad town in the past, but what I really don't understand is that anything that happened in the Past changes what happens in the future, right? but then again... it IS mario...
I was kinda hoping for a Oracle of Ages version of Mario with Partners in Time, but sadly that was not the case. I still enjoyed it though.
I didn't complete SS or PiT, but SS was more fun.