they can also be considered as creatures joining your army))
let's say you have one slot available, who would you take? ))
yes, knights and nagas are good in attack, and their other stats are also decent, they move far, but they don't fly... like many others with worse stats)) ... I rarely need flying units, even during a castle siege... usually, either my catapult is upgraded or there are few troops in the city... and in general, even if there are many of them and they are all in the castle, I don't send flying units ahead... they will be killed quickly there... so I'd rather take strong infantry than weaker flying units))...
but usually, the weakness of the stats of one creature from one castle and a creature of the same level from another castle depends on the stats of other creatures of that level)) for example, among the 6th level creatures, death knights are the strongest, but cost dragons are one of the weakest 7th level creatures, the same goes for wyverns and gorgons, minotaurs and manticores, etc.
... and everyone has different tactics)) these types of creatures are good for my tactics).