Titans in Heroes of Might and Magic III had 300 HP, but in Heroes of Might and Magic V they have 190. Angels and Black Dragons also became weaker...
But in Heroes of Might and Magic V, level 6 creatures are stronger. Ents, Wyverns... they have 170-180 HP, while in Heroes of Might and Magic III, Dark Knights had 120 (the best HP stat for level 6 creatures).
Regarding the topic:
I always choose based on my preference, not on strength. I like Angels and Titans at level 7.