FF love and hate is about two things.
1: Which game you started on, which game you first understood for what it actually was and took as a part of the genre of rpgs. Many people have that first game be their favorite, I do that, FFVIII was that for me. I did play VII a bit before it but I was too young and my being not a native English speaker prevented me from understanding anything about it, I did revisit it later though and I do like it a ton but not as much as VIII. I loved the story, was completely immersed into the world and it was what opened the window to the world of RPGs for me, thus is my favorite game of all time.
2: What game is the most different from #1. I loved VIII, X, XIII (in that order), I disliked XII and to a much lesser degree IX (i just really hated Trance as a system, way worse than drawing magic IMO). Common elements between those titles are obvious, i like the ones with heavy focus on stories, romance, animelike themes and really meaningful endings. XII was lost due to the gameplay being like XI but without the online interactions and dumbed down considerably and IX...like i said...i mostly liked it other than the trance system and the terrible ending which gave me zero closure, it was like a fairy tale lol. Even the retro theme was not all that much like FFI-III, it was like FFVI which was decent (i played it ages after it was first released so it didn't have the impact it would if i played it when it was new...but i was like 7 at the time and like i said i wouldn't have understood a word)