The Blue Blue
I would like to argue that illusion clones could effect my ability to strike the opponent. In order to illustrate this, I give you the following example.
Kenta produces 3 illusion clones. They surround Sai and then all of them move forward as if they were going to attack. This effects Sai's ability to block my attack because he isn't sure which attack is the real Kenta.
Also, while the clones are illusions, in theory they could still be used to cast a genjutsu technique.
The problem I have at the moment is that with things how they are illusion clones make zero sense. Why would I bother ever using the illusion clones when I could instead make real clones at slightly over double the cost and have them offer not only defensive accuracy buffs, but also offensive accuracy buffs (already twice as useful) as well as a damage buff, and as well as 20 additional damage points?
Similarly, assuming that "Clone" is not a buff all of it's own and instead it is the buffs that it grants that count towards your buffs, why would I ever use real clones?
Buff
Damage +50 to ninjutsu (1 point) +12 Accuracy ninjutsu (4 points) does two and a half times more damage and a little more than half of the accuracy. Similarly, I can chose how to spend those points and how to split them, making the standard buff more versatile than a clone. What's more so, is that if I made it more specific and said that it only worked on lightning skills. it would be +75 damage, and +16 accuracy, and it doesn't appear that the clone's buffs can be narrowed in that way.
Clonse are buffs of there own.
A single level of any type of clone is more effective than spending levels in a global buff (a limited version buff can be numerically more beneficial but as said it's limited).
For example 5pts in buff is +10 accuracy or +15 defense accuracy.
Illusion clones and real clones give more than this, the catch? They can be destroyed making the jutsu less effective or have to be re-activated more often thus costing more chakra.
Now as for real clones compaired to illusion clones and the benefits of each.
Illusion clones are better for maxing your defense accuracy, but real clones give an overall higher global buff.
For example, a level 100 skill.
All invested into illusion clones would give (2pts = +20, 20x50 purchases =) +1,000 defensive accuracy.
All invested into the real clones would give +400 attack accuracy and defense accuracy, +400 damage.
The real clones give a total buff number of 1,200 slightly higher than the illusion clones, however it's not maximized for optimal buff potential as the illusion clones are, and that's the reason both have there ups and downs.
Your paying less per point of buff for the real clones (since you get +60 per 5 pts where as with illusion your getting around +50 per 5pts), but the illusion clones as a result will maximize efficiency.
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As shown earlier normal buffs would be more costly than either of these in terms of chakra spent per point of buff.
However the diffence is that as your struck in combat (if you succeed only by the % granted by the clones, ie if you'd get struck had you not had them activated) the clones buffs start to diminish.
So normal buffs are NOT more efficient, they grant less buff bonus per point spent but have the advantage of lacking the degrading quality the clones have as a drawback.
Your example is a downright misrepresentation as it limits it to one style.
Sure, it does an efficient amount compared to clones (for your one chosen style)... but it does 0 bonus to every other type of damage or accuracy. If your a character that's not 100% nin (focusing like that as shown before can be a drawback do to defending against different types and limited effect choices) then the clones are more efficient until they start to degrade.
To put it simply, you can't make them the same as normal buffs in terms of exact effiecency and exact drawback or they'd be the same exact effect and pointless to have. As it stands they're situationaly better and situationaly worse, as they should be.
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As for why illusion clones don't give an attack buff. Yes, it would make some logical sense to give them an overall accuracy buff, however to balance the numbers in game mechanics it was left as only a defensive measure.