Necropolis or Castle (Which one is stronger?)

As far as I know, prayer doubles the damage dealt by a unit... I believe that the main strength of Haven lies in archers + knights + champions, in such a combination. Just archangels alone aren't that powerful.

Your post shows that your knowledge of Heroes is still limited (don't be offended! :)), although they are probably truly boundless, and it seems impossible to learn all the nuances of the game... Prayer increases attack by 4, and creature speed by 50% (acceleration by 100%). Regarding the main strength - in principle, you can talk about this for a long time and persistently, prove something, argue, etc. Personally, I would prefer royal griffins to knights (but let's not argue about which is better - both are good, and each in its own way, I just stated my version...;)).
In general, the strength of Haven is probably not only in the units, but also in development, and there are also excellent heroes... ;) (Mullich alone is worth something...)