You post was exactly the kind of thing we like to see here: back and forth discussion on game mechanics for the betterment for all. Until the last paragraph. That didn't need to be worded that way. You could have asked for supporting logs in a much more civil manner.
Do you use the 4-set bonus for pws?
As far as I know, Smite can also crit and create Aegis on people, that would increase the hps of the atonement sequence a little, but it's not really relevant to the end result.
The Problem I have with these two builds is, that don't think you'd heal in a real raid situation with such a rotation. And you don't consider hpm (of course in the current gear, Mana is not a real problem). I would also see a problem when you consider each Smite to hit the tank, since it's a smart heal it is also going to hit melee thus healing somebody without grace. You should also consider that a shield, penance sequence will also provide BT to your next smite.
When healing with atonement I somewhat prefer to use hasted penance - greater heal sequences, if there is need. You completely leave out gheal, but at the moment it's a lot better than heal, especially with BT. And remember that you can pop Archangel for more healing + mana (you lose heal on Smite, but you gain the heal for penance/ what else) If the tank is low in ICC I'd surely throw in a fheal.
I don't believe, Discipline healing is so much about rotations but rather choosing the right spells at the right time. (Or just plain Shield spamming if hps really counts, that's still where we rock)
I do consider the 4-set bonus I get the PWS value from the tooltip and I have 4T10 on. I also take into consideration aegis from atonement and haste from BT in all rotations.
Why you would not tank heal with these rotations? I don't see why not. HPM Does not need to be considered, these are the most mana efficient rotations for each build. Especially heal/pws/penance is by far the best HPM you can get while healing the tank. Both smite (15%) and heal (9%) are considerably cheaper than flash (28%) and gheal (27%) and on top they get both an HPS and an HPM boost by their secondary effects on weakened soul and penance.
The problem with atonement not hitting the tank is certainly an issue, but I think that is slightly beside the point. One of the objectives of this exercise is to compare a heal and an atonement rotation. These are the basic rotations that you would tank heal with. Naturally other spells will be cast if needed, but as the encounter demands.
I left gheal out intentionally. It does not belong in the basic tank healing rotation. The basic rotations take advantage of two things a) Heal reducing the duration of weakaned soul b) smite reducing the CD on penance. Gheal does neither and it costs more mana. In fact discipline does not have much use for gheal.
I strongly disagree that discipline does not have a tank healing rotation and that you have to pick the best spell for the situation. The best spells for tank healing are pws and penance and you have a rotation based on which fillers to use in between. Heal and smite are the cheapest fillers, and they decrease the CD of penance and PWS. Gheal and fheal have higher HPS but also much higher burn rates.
PWS spam is raid healing. That is an entirely different senario. If you believe that you have a tank rotation that is better please post your numbers here. Your intuition and subjective experience of what works well are sadly not suitable for quantitative comparisons.