Your suggesting that Rotation users can reach unlimited speeds, and have an unlimited chakra to constantly oppose ameratsu and reach the power of shinra tensei - which would eat away at the chakra as you said. But this spin cannot be maintained for an endles amount - whilst ameratsu seems to last a much longer time. If it did fall to the ground, it would hardly be 'harmless' and sasuke can still control those flames as well as summon more. Also im not exactly sure how chakra being expended at a larger rate in order to expand the rotation's reach would make it stronger, it might be the same as before the extra chakra use - but expends too much chakra and is not sustainable.
in regards to your comparison between shinra tensei and rotation, you are completely overestimating the span and power of the rotation technique. Rotation is meant to supplement the small blindspot that the byakugan has, and act as a general defence. Its not unbreakable. It also does not effect the ground underneath (and possibly even leaves a spot open above the user).
Rotation is hardly a 'spammable' technique - it uses every chakra point in the body to release chakra while rotating - draining physical and chakra energy. It takes time to initiate and wears the user consistantly - getting back to my point of you assuming neji etc have unlimited charka...etc.
Shinra Tensei on the other hand has been used by pein within succession - which seems to totally disregard any form of chakra limitation. The 5 second limititation - although a weakness, is not totally justifyable as the one means to success against an ameratsu - if 'spamming' ameratsu, sasuke could take anyone out.
1) Yes - but so does Rotation
2)This isnt Pein vs Neji, its Rotation Vs Shinra Tensei
3)Yes, once again, not Pein vs Neji
4) 5 seconds is hardly a great period of time, Rotation cannot be used in excess - whilst Shinra Tensei seems to be limitless.
now to the point of this arguement.
Sasuke vs Neji
They are both genious', they analyse everything consistently.
Sasuke has use of Genjutsu, and ninjutsu which is way more powerful than Neji's and any lack of power in taijutsu is accomodated for within susano'o.
You also seem to be forgetting that Rotation is a DEFENCE ninjutsu - although possibly used for offence - the abilities that Neji use are totally outscaled by Sasuke's abilities - primarily susano'o.
are you forgetting that sasuke has 'sasuno'o arrow' ?
He doesnt need to get near Neji to fight him - nor does Neji have anyway of using his chakra targetting taijutsu through susano'o and any long distance format.
I never suggested that they could rotate at unlimited speeds. I said that the main part of the defense comes from the spinning that is required to maintain the jutsu. I also never said that they have unlimited chakra in which to use such techniques. I stated that the users never pass out from chakra exhaustion after the just use. Neji has used it many times before in a consecutive manner, despite its chakra consumption rate and come out with minimal fatgue, leading to to the conclusion that they have fairly decent chakra reserves.
As I said before about rotation and amaterasu, If sasuke isn't around to manipulate the flame anymore, then amaterasu would simply fall away or dissipate, leaving the user untouched.
When using more chakra to create a bigger dome, one must first release more chakra at a faster rate. The extra push to release more chakra gives it more outward thrust in which to counter any incoming projectiles, and thereb increasing its overall strength. It never loses strength because the main defensive power comes from the centrifugal force during the spinning that pushes the chakra outward while at the same time rotating it to create a repulsive barrier.
I never said it is an unbreakable defense, however, it would require more than just brute force to "break it". You could use the fight against naruto against me, but I have already made a solid statement as to why that wouldn't count as a true rotation.
Contrary to your statement, it actually does affect the ground underneath as it leaves a crater whenever it is used. The part about having a weak point above it would possibly only apply to the very tip of the rotation, since that is the point in which the user is spinning around and where the centrifugal force is weakest. However, it would have to take a very small projectile with a lot of power to get through it.
It is "spammable" because it only relies on the users chakra and their chakra control. It takes little time to use since the effect starts once the user begins rotating and ejecting chakra. There are no handseals involved since the technique is only done through the superior chakra control of a hyuuga. It does consume chakra at a consistent rate, however, because the user can continuously rotate while releasing chakra, it becomes a continuously defense, unlike shinra tensei which only asts for a second.
Pain, on the other hand, has huge chakra reserve, and does not have to worry about using to much chakra whenever he uses the technique. It is only spammable to a point, since it can only be used once per 5 seconds. By the way, sasuke has spammed amaterasu before and taken out plenty of people with it.
I was refering to the large scale when I mentioned the side effects.
1)Rotation doesn't cost nearly as much chakra as a large scale shinra tensei.
2)I know this is Shinra tensei vs Rotation, but we have only seen pain use this technique, and therefore this would is just a reference to my point.
3)This shortens the lifespan of ANYONE who uses this technique on a large scale
4)Actually the large scale shinra tensei required a MUCH larger recharge time than a regular one. It was already said that the technique takes longer to recharge depending on the amount of power that is used. The one Pain used on Konoha required him to wait at least several minutes before being able to use it again. Again, shinra tensei is used by pain, who had vast chakra reserves, compared to a hyuuga, who has much less. Of course it would seem that shinra tensei is more "spammable", but only because he has the chakra to use it over, and over again. If you give the same amount of chakra to the rotation user, then it becomes just as "spammable" as shinra tensei.
5)Another thing is to note is that it takes longer to revive the paths after this technique is used.
You are basing the spammability of shinra tensei solely around the amount of chakra pain has in comparison to a hyuuga. As I said before, they both require a great amount of chakra, but, if put on the same level, large or small, shinra tensei only lasts for a second, while rotation can be used continuously.
I understand your points on Sasuke vs Neji and I agree with you to a point. I never forgot that rotation is a defensive jutsu and has offensive purposes as well, its my favorite jutsu after all.

Anyways, as you said, sasuke has much greater offensive power than Neji does in with his MS-particularly susanoo. I also never forgot about the arrow, though I am certain that rotation is perfectly capable of deflecting it. Neji also has vacuum palm, which is a long range technique, though it likely wouldn't do much to susanoo.
I'm not saying that Neji will beat Sasuke with MS and certainly not in EMS, but he does have a fighting chance-though mostly with just MS since his techniques are more chakra costly then. Sasuke with just 3 tomoe can be beaten by Neji or be drawn to a stalemate IMO and I have supported my ideas very well in the past.
Anyways, I'm glad that hasn't been any flaming so far! xd This is going pretty well if I do say so myself.
