Folksoul said:
Okay, in no particular order....
Youngest party member has mother die because of older party member with trench coat doing something foolish.
Party's moral choice is "die, or everyone dies."
Cannot control party in combat aside from leader, only influence types of abilities used.
I can go on for weeks here, and have, to the great irritation of my friends. They are, in a general sense, THE SAME DAMN GAME. That's why I like 13 and its spin offs and not so much the rest of the franchise.
A chunk of those feel pretty coincidental. JRPGs having a history of not revealing anything substantial for the majority of their plots if not until the final hour. The supporting traitor? That one's been around since the SNES days if not earlier.
"Antagonist who comes to respect/sympathise the heroes after being defeated and commits suicide. (Raag Rosh-Chidori)" Chidori didn't support or sympathize with the heroes as a whole though, she loved Junpei, and only acted in support of him alone. On top of that, it's another pretty common trope in both the honorable warrior type and the antagonist love interest type.
"Ambiguous bordering on blatant homosexual romance between two party members." Again, coincidental since I don't think Shinji or Akihiko were first written as a woman and then changed at the last second like Fang was, even then the relationship never crosses over into that boundary unless you're looking at it way too hard.
"Party members have a large character development set-piece(Eidolon Fight-Persona Ascension)" Revelatory battles and/or cutscenes? Really? Those are properties so unique to these two things that it warrants saying they're nearly identical games?
"They are both 50/50 grinding and cut scene." I think you can fit all of Persona's cutscenes into the length of one or two of XIII's... I mean, I guess that depends on what you define as cutscene but the day to day sim stuff were part of the gameplay, hell you could even call them a type of grind since they were another way of unlocking more persona and many people treated them as such, skipping the dialogue in them and looking up guides to pick only the best answers.
"Both games have personality specific combat skill trees for each party member." Classes. The word you're looking for is classes. Persona didn't invent them and XIII wasn't trying to be like it in their use of them either.
"Sh*t crafting system that is nothing but a money sink.(Persona fusion- Trapezohedron farming)" Except the Persona fusion is central to the game, you won't get very far into the game at all without using it, and it's entirely possible to not put a cent into it. Trapzohedron gives you those shiny final tier weapons but it isn't a necessity.
"Constant insta death from generic encounters if battles are not initiated properly. (Active persona weaknesses-Paradigm deck mismanagement)" Though one comes from the standards of its franchise and the other is from poorly defined systems, and have entirely different executions.
"Ice queen becomes mother figure that increasingly fetishized in subsequent appearances." I know the whole ice queen thing, but mother figure? Where does that play into them? Older Sister type, sure, but mother figure? Lightning's fetishization was always there, it was just that Toriyama's muzzle got looser and looser as the years went on. Mitsuru on the other hand got one bump up between appearances and it was done to Akihiko as well with the constant shirtlessness and innuendo-filled dialogue. All of it intentional and played for laughs. One was done out of silliness and the other was dead set the director jerks off to this character what the fuck are you doing Square... er... ness.
"Arbitrary grinding cap(Crystarium levels/ Dungeon sickness)" Welcome to JRPGS! No really, you're naming a lot of things super common to the genre and then acting as if they are wholly unique to these two games. That may explain your friends' annoyance. Only ones where nothing comes to mind are what I left in the initial quote. Even then the way the games handled some of those, revenge bent kid for example, were handled pretty differently and had wildly different outcomes.