Agreed.

Although I found Seymour more likeable than Delita. Delita had lost all my respect by the game's end.

I guess it partly has to do with the way the game reveals their backstories. In FFT we get to see Delita's tragic backstory early on and then gradually we learn about his ruthlessness. In FFX we initially don't have much emotional investment in Seymour and only later do we find out about his tragic origins.