Game from 1978: Why does this fuseki position favor black?
It seems that the move to play for White is an extension on the upper side or in the lower side. Clearly, the lower side is more interesting for the following two main reasons.

$$W
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . 1 . . . . X . . . . |
$$ | . . . , O . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . X . . . | 
$$ | . . . , . . . . . 2 . . . . . , . . . | 
$$ | . . O . . . . . . . . . . . . X . . . | 
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . |  
$$ ---------------------------------------



Black's shimari in the upper right is low. Black is thus not interested in playing in this area  now.
Black has a perfect extension at 2. His moyo is developing perfectly.


Consequently, White wants to play as in the following diagram.

$$W
$$ ---------------------------------------
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . O . . . . . . . . . . . X . . . . |
$$ | . . . , O . . . . , . . . . . , X . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . . . . . . . . . . . . . . . . . |
$$ | . . . O . . . . . , . . . . . X . . . |
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . X . . . | 
$$ | . . . 2 . . . . . 1 . . . . . , . . . | 
$$ | . . O . . . . . . . . . . . . X . . . | 
$$ | . . . . . . . . . . . . . . . . . . . | 
$$ | . . . . . . . . . . . . . . . . . . . |  
$$ ---------------------------------------


However, Black has now a very good erasing move at 2. White's moyo is therefore not as good as Black's position.

In conclusion, even if White plays its best move, Black keeps the upper hand which means that the fuseki favors Black by a bit.