It can be a lot faster, but it can also be slower. With databases, the answer for almost everything is "it depends." Here, it really depends on how big the table is, how many rows you're updating, what the indexes are, how much RAM is available, etc.

My point is that, in a vacuum, you can't really say anything about what the performance difference will be. Yes, you can certainly find instances where the performance is better, but it may not be much.

My point is that the complexity of writing the statement is non-trivial, and unless you have a good reason to you shouldn't use CASE. It shouldn't be your first choice, is all I'm saying. For example, the example you provided here is not even valid SQL. It should be:

    UPDATE TABLE place 
    SET rating = (
        CASE WHEN id = 1 THEN 25
            WHEN id = 2 THEN 94
            WHEN id = 3 THEN 16
        END
    ) 
    WHERE id IN (1, 2, 3)

Keep in mind, I also said: "If performance becomes a problem on this query, you can fix it later when you can focus on just that one issue and understand the specific problem much better."