I don't think it'd ever be better because you're always writing off the loss, the difference is the size of the loss. It's better to, e.g., get 10K back out of 100K investment and claim a 90K loss, versus getting back 0K with a 100K loss claimed. You're only getting back your taxes from that 10K difference in losses, versus getting the 10K back. The delta would always be there.

Please excuse my ignorance, but I don't understand this.

Scenario 1: I have $100 in gains this year. I owe $30 in taxes. I am left with $70. (Say $100 is 30% bracket)

Scenario 2: I have $100 in gains this year. I write off a $10 loss. (Say $90 is 25% bracket). I owe $22.5 in taxes. I am left with $67.5.

Is it the case that writing off the loss is better, if you can be bumped so far down the brackets that (gains - loss)(1-lower_tax_rate) > (gains) (1 - higher_tax_rate)?

No, it's continuous with no edge effects like this because only income within a bracket is taxed at that bracket.