They do that so new and experienced players can all play together and no one is super overpowered. If you combine your upgrades right you will notice a difference though, I like to use reload speed, extra ammo and more damage together for the best outcome.
I do not agree to the low difference in health points that the health upgrade provides when used though.
but I think that its a very good experience for new players in the sense that this will be motivating to them to make their best to be able to beat the the most experienced
I think they purposely put health upgrade at the end and make it small so it doesn't over powered.
If master level player already strong and has 2 other upgrade then put extra 25 health, it will be almost impossible to kill him.
We can use it for low health character (imp, sun flower, rose, soldier) so enemy need to put ONE or TWO extra bullet to kill you.
That extra bullet could make big difference. When I use health upgrade on imp, I feel like I'm invincible and much harder to die then before.
If you play long enough, you know how many bullets needed to kill an enemy character. Sometimes, you wonder why this enemy is not dying yet. It used to be die by now. That could be because they use that extra health upgrade.
Some variants are fairly poor without the proper upgrades. Tank commander, iron citron - reload upgrade x2; any rose - homing; frozen citron - ice; hotrod chomper - digestion x2; alien flower - spore cloud upgrades. Etcetera.
Then there're the ones that are utterly useless - iron citron, armor chomper - health... As noted above, a few characters benefit greatly from the health upgrade.
