>> Scoring system for unfinished roads and buildings
The Castle: Conditional. A player only score points if he/she got; a) got the correct bonus/es and b) got the most workers located at the largest unfinished project/s covered by the corresponding bonus/es. 'Passive end game bonuses' can be acquired to get victory points for the largest (or longest) unfinished; tower, house and road. NB! The english rules got an error in the translation: An unfinished road with a fountain only counts as 1 point (Dr. Knizia have confirmed this).
Carcassonne: Yes unfinished cities score, but with reduced points. You need equal or more workers inside the city to score points in the end. The player with the most workers gets the points alone.
>> Scoring system for merchant/farmer - completed buildings/cities
The Castle: In The Castle variant you put merchants on the field to get victory points for markets that is attached to the field. A player must have the most merchants on the any single field with markets to score points! Markets scores 3 points each, 4 or 5 if you got one or both of the bonuses (Note: Bonuses apply to your largest market area only)
Carcassonne: A player scores victory points if he/she got equal, or more farmers, than the opponent on the same field connecting to one or more cities. Each city rewards 3 farmer points. The player with the most farmers gets the points alone.
>> Scoring system for the roads
The Castle: 1-6p pr. tile! In The Castle you score 2 points for each road tile if one or more fountains are connected. Normal roads score only 1 point pr tile. Both types of roads must be completed to score points, and the score can be increased by one or two bonus tiles (x2 or x3). Unfinished roads (see the first column). A single threeway-intersection road tile that complete multiple controlled roads can in theory give max 10 (2+2+6) points. But this is extremely rare.
Carcassonne: 1p pr. tile. You score one point for each road tile if you got equal or more workers on it. This counts for both finished and unfinished roads. The players with most meeples on a single road scores the points alone.
>> Scoring system for completed houses/towers/cities
The Castle: The Castle features both houses (red ceiling) and towers. 'Closing' towers rewards 2 points pr. tile, while houses gives only 1 point. 'Usable' bonuses, that can be acquired from the castle wall, can increase the total score if you use them in the same turn the corresponding building/s are closed. Players do not score points if both of them got the equal amount of workers connected to the building when it's closed.
The bonuses can only be used during your own turn! Max points for a tower tile with bonuses is 6, and 3 points for a house tile.
Carcassonne: Vanilla Carcassonne rewards 1 point for each city tile and 2 points for each city tile with a shield, and these points are rewarded for unfinished cities also. If a city gets enclosed the player scores 2 points for normal city tiles and 4 points for the city tiles with the shields. Only a player with the most meeples in the city scores points. Equal number of workers rewards both players points.
In The Castle you start with one less meeple, 6 vs 7. Carcassonne - The Castle rewards the player with the largest house, called the keep, with a bonus = The largest open space inside the castle walls usually brings between 5 to 13 points at the end of the game. Also the bonuses on the scoring track are not featured in the vanilla version. The Castle got 60 tiles ('66' counting the starting areas) vs 71 (72 counting the starting tile) tiles in the orginial. However the starting number of meeples is the same, 7. In the original Carcassonne the tiles got 19 varations, in The Castle 48.
The fixed walls limit the playing area and makes The Castle much more 'table friendly'.
The benefit and importance of getting many bonuses in The Castle variant leads to less contesting for projects, especially in the first stages of the game. Contesting projects in The Castle mostly happens in situations where players got something big going on. A skilled 'Castle player is even more eager to take steps preventing the opponent from connecting to his largest projects due to the scoring system with zero points following a tie in control. 'Helping' the opponent to finish his/her projects is much more common in The Castle due to the keep and bonus system. In both versions you achieve a lot by stopping the opponent from finishing projects, and the rewards are even greater in The Castle variant due to the fact that unfinished projects don't score points at all unless the players have the correct bonus/es. The fight for getting the largest keep, and 'the end game battle' to increase or reduce the largest open space, is of course another notable difference. Due to the overall number of delicate considerations of where to put the tiles and meeples, and when to use or deny bonuses, I would consider The Castle to award skill the most!