Everything scales with INT, and INT scales better due to Rank bonuses providing 10% increased INT per Rank.
The only thing that does not is Stone Skin. Mass Heal also scales with INT at the same rate SPI does. Aspersion also scales with INT since it deals Magic Damage. Stone Skin and Deprotected Zone are the only things that require SPI scaling.
The benefits to going INT over SPI in my mind is that for supporting, Heals and Aspersion scale with INT just as much as SPI. Offensively, Heal and Cure get double scaling from INT, making it useful offensively while soloing whle not hampering your ability to stay alive to support parties with. INT will also get 70% more stats than the same amount of SPI, so comparatively, those going pure INT will have better heals than pure SPI
Deprotected Zone will get more Defense reduction with Spirit, depending on how much Defense bosses get, a full Spirit character can make the most out of this, as well as maximizing Stone Skin’s Block Rating, but that’s about it.
I think what classes are available that are missing will be pretty important as to which stats will be overall better, unless they make some changes to how INT and SPI function, as they’re both currently lackluster in what they do.

