From 20 to 25: 28 Candy 31,000 Dust
25 to 40: 220 Candy, 194,000 dust.
So would you spend about 13% more candy, 16% more dust to switch 15 Stamina/13 Attack to 15 Attack/13 Stamina
At 40, the odds of hitting a break point with 15 vs 13 attack is pretty small.
At 40, the odds of surviving a move due to the extra couple hps to do another move, are pretty small.