A THREAD FOR NEWCOMERS!

I asked the question incorrectly... Which Castles are considered strong, and which are weak?

It all depends on the map you're playing on.
For example, on some M-U maps, the Tower is considered one of the strongest Castles. Why? Because it always has a native secondary Castle without a Fort. And this means a good bonus for your main stack - Gremlins.
But on larger maps, the Tower usually doesn't make it into the top three.
One of the most stable Castles, good on most maps, is the Castle. It has the largest variety of buildings, excellent troops at almost all levels, an increased bonus for the external stable, the ability to create both ranged and melee main stacks, and so on.
The Rampart is also a versatile Castle. It has troops to suit every taste, fast or durable, and good damage-dealing ranged units.
But the Dungeon is very dependent on both the map and the setup. The presence or absence of a key resource node. The richness of the map and the starting difficulty level. I remember playing against an equal opponent, and my secondary Castle was developed to the same level as his main Castle, while his main Castle already had Manors (the game was at 200%). He was just unlucky. Therefore, the Dungeon is not as versatile a Castle as the previous two. Besides, the Dungeon is quite heavily dependent on Shakti; if there is no Shakti, it can be difficult to advance on a resource-poor map at 200%.
The Swamp also depends on the map. In principle, it's a strong Castle, but it requires tactical skill, and its strength increases significantly if there are many Hives - because you can upgrade Wyverns, and morale doesn't decrease!
The Stronghold is an ambiguous Castle; on resource-poor maps at 200%, there may be difficulties at the start. After all, it's an attacking Castle, but you need something to attack with! In the unedited version, considering the number of Goblins and Wolves, it's not an easy choice. But almost always, Birds are built, and several times I've built 117 creatures on a 200% map!
The Inferno. On resource-poor maps, there are problems with the start. In general, playing with this Castle requires a certain level of preparation; it's not that simple. Ifrits do wonders on the first level, of course, but you can't play the Inferno mediocrely. Either you have to play it well, or you should exclude it. In difficult situations, it makes sense to think about "small Hydras."
The Necropolis and the Conflux. Don't play them yourself or let your opponent have them in the early game. It makes sense to first gain experience playing with the Necropolis and Conflux heroes, and then switch to the Castle. In games that don't have tournament significance, be sure to try playing as the Moon, as often as possible. Also, in several games, you can use a Necro strategy; this is something that every player should have in their arsenal. However, in my opinion, it shouldn't be a universal weapon; sooner or later, you'll pay the price.

Conclusion: decide on the map. On almost any map, the Castle will be a good choice. The Rampart will also work in many cases. Don't let your opponent have the Necropolis or the Conflux.