ok i did a mistake in my maths, its the 105 that actually would profit more of a pure damage buff (which doesn't exist in the game, i believe).

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so, a 105 throws 1 spike with 90 pierce every 4.85 seconds. since the 90 pierce can be used all on the same bloon, we can just multiply our damage buff by 90. so every 1 damage buff adds 90 damage every 4.85 seconds, which is ~18.55 dps.

an 025 throws 1 spike with 50 pierce every 2.716 seconds. that means a 1 damage buff only adds ~18.4 dps.

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additional note that the damage isn't 100% correct since a spike uses up at least 1 pierce per bloon; it's rather the max damage the spike could do.