What's the difference between Screen Horses and the Reversed Palace Horse as defences to the Central Cannon?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws for movement, checkmate and both repetition rulings: a side that forces a repetition by perpetual check or perpetual chase loses rather than drawing. The chase half has not been validated against the official casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it before publishing.
Direct answer
Screen Horses (屏風馬) and 反宮馬 (Reversed Palace Horse) both bring out two horses that guard the central soldier. The difference is one cannon: in 反宮馬 it goes to the advisor's corner, between the horses, where it defends them both. That makes the structure more solid, at the cost of a slower, more cramped development than Screen Horses, the most natural and most studied way to meet a Central Cannon.
What you get with Screen Horses
Immediate, efficient equality: the same move that develops a horse also answers the Central Cannon's first threat, which is exactly why it is the most played defence in the game. The cost is that it walks straight into the most deeply studied territory in xiangqi theory, where a well-prepared Red has the most to work with.
What you get with 反宮馬 instead
An extra defender for the horses: the cannon at the advisor's corner covers them both, so a move that blocks a horse's leg does not also remove the defence. The cost is a move of time and a cannon standing in its own pieces' way. See the Reversed Palace Horse for the mechanics; neither defence is objectively better, and the choice comes down to whether you value speed or solidity more.
Related questions
Which should a beginner learn first?
Screen Horses, since its plans are the most natural and the most widely explained, making it easier to learn from games you will actually see.
Can I switch between the two depending on the opponent?
Once both are genuinely understood, yes, but learning one deeply first is more useful than splitting attention early on.
.