Which level 7 creature is the best, and why?

Well, you know, you might as well ask how Pascal works. I've only played Heroes Online about 5 times before visiting this site... The rest is just computers and hot-seat games.

See, you admit you don't know everything; in short, what morality is – you can read about it (where? – I think it's unnecessary to say), but if you're too lazy, then:
morality "+1" is only a 10% chance that this creature will get an extra turn, "+2" is accordingly 20% - yes, for example, in the bank, this is a huge advantage, but in Heroes, it's not that important - you can check it yourself, give +1 to one hero and +2 morality to another, the difference is almost negligible;), let's pit our competitors against each other (Dark Druid and Archov) :)

You'll say I checked and it's not true... Have you ever encountered a situation where you have archers in your army (for example, with Adela) but only blessings in the spellbook?

I probably won't make you happy - NEVER will magic give priority to the turn. If you cast "blessing" on the second group of archangels (for example), they will still go second on the next turn - this is undeniable! Before making such claims, check it (you also said that dragons would defeat archangels :D)

If you haven't played Day of the Hurricane, that's your problem, but in my opinion, this map is a real competitor to Gift2001, and how many points will Armageddon inflict? And what if it's a dragon set? And in general, I think combat magic is good at the beginning - but then curses and blessings are the best...

And what does it matter whether you played it or not, remember what we were discussing? We were talking about the fact that you said you can cast anything on an archangel, but in a real playthrough of any map, immunity will be stronger, in my opinion :)

Will we argue for a long time?

No one is arguing, we're just discussing :) - by the way, there are probably some benefits to this kind of "discussion"...