Baldur’s Gate 3 is a story-rich, party-based RPG set in the universe of Dungeons & Dragons, where your choices shape a tale of fellowship and betrayal, survival and sacrifice, and the lure of absolute power. (Website)
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Yes: If you're out of spell slots at the base level, but have higher level spell slots remaining.
It's also possible that upcasting makes your spell more resistant to an enemy's Counterspell, depending on how Larian implemented the mechanics. I believe this would follow 5e RAW, but I haven't tested it in this game.
Edit: Rephrased for clarity.
I thought RAW couunterspell ignores if a spell has been upcasted. I remember something about it only taking the original spell level.
The Player's Handbook says this:
When a spellcaster casts a spell using a slot that is of a higher level than the spell, the spell assumes the higher level for that casting.
Counterspell's description says nothing to override this.
Some scale and some don't. At least on the PC version it tells you if there is any benefit to casting with a higher spell slot.
Because you've already expended your spell slots for that level.
No, if there’s no stated difference for upcasting then there’s no reason to do so