I prefer something unique, coherent. I dont have any preference in term of graphic, setting beside good writing (which, i know, can be hard to find in games sometimes)
If you have any other rpg in mind, let me know
I try to separate my bias in this case since I vastly prefer VIII in almost every aspect.
As a safe option when it comes to writing I think you'll prefer IX to VIII. VIII has a great story and cast but the game is heavily reliant on players interest in exploring and interacting with the world and NPC's. The game even has scene differences depending on choices made earlier that offer more information and background to characters. It's got a massive focus on making the system, world and story connect together so while the main story still makes sense on it's own it doesn't always come across fully without that level of interaction outside it.
IX DOES have it's moments of bad writing(I would say most FF games do) but the majority of the game isn't overly complex or nonsensical so it definitely is easier for people to find more coherent than VIII.
When it comes to battle systems IX is as traditional as you get. Armor/weapon system, leveling makes you stronger and grinding is a thing if you want to overpower fights. VIII is more unique in that enemies scale to your parties average level and magic is acquired by drawing from enemies or refining items into spells. There isn't a traditional armour system but instead spells link to character stats and boost them similar to equipping armor. Same with elemental and debuff protections.
I do think you should eventually try both but right now I understand it's down to wanting only one at the moment so if anything here interests you grab what you think sounds best.
By the way, I don't know if soundtracks are important to you when it comes to a new game but if it is you should definitely listen to a few tracks from both and see which style you like more. They both are very different. We could also link some here if you don't want to search in fear of spoilers.
Edit: Also for a recommedation play Tactics Ogre đź‘€