Don't get me wrong, I really like the principle of faction diversity through building HP differences. But I still don't get the strange progression of the HP (mostly resource buildings) and I think it is a very good question. To clarify what I mean:
(Mexes and pgens)
At T1 UEF HP is 54% higher then Cybran
At T2 that difference is 39%
At T3 it is 50%
So all in all, the difference scales roughly lineary.
The difference between Aeon/Sera and Cybran however does not.
At T1 Aeon/Sera HP is 20% higher then Cybran (roughly in between)
At T2 that difference is 6% (why?)
At T3 it is just 3% (again why?)
Just to clarify, I would have expected something along the lines of 7500 (t3) and 2160 (t2) for Sera/Aeon to keep it at roughly 20% when going Cabran->Aeon/Sera->UEF at all tech levels.