Which castle is advantageous against the Stronghold?

If you have similar conditions, in my opinion, the optimal option, as mentioned above, is Inferno (Nimus) and Necropolis (preferably Vlad). With proper development of the first, you get a very strong attack, extremely high initiative, and a huge number of summoned creatures (in my opinion, Inferno does have a certain drawback in that you have to sacrifice defense :( personally, I prefer to develop talents in chaos magic or leadership). When playing as the second, you get, in fact, an immortal and constantly growing army with relatively low city development.

P.S.
To be honest, this is based on personal experience; I found that these factions are the most enjoyable on long maps.