Black has just two pawn chains, white has three. White is also a bit weak on the dark squares. He is missing his dark squared bishop. Still it is probably just a slight advantage for black because white pieces are placed ok and the bishop g7 doesnt attack anything (yet).
Replace Nc3 in the start position with a bishop and white is better. The bishop protects d4 and b4.
A space advantage is irrelevant if some of the advanced pawns can be exchanged by pawn levers, here c5 and a5, as
@Sarg0n #3 already said. Then files will open and the remaining advanced pawns, now isolated or backward, can be attacked from the side or from behind or from the front via the open files by opponent pieces. This is especially dangerous if the player with less space has a development advantage, because an advanced pawn can be attacked more quickly than a pawn in the starting position. This principle was found by Steinitz. He developed his theory of defence, which is the base for many modern openings: The pawns in the starting position are the best defenders. This is right, but Steinitz sometimes exaggerated and refused to bring the pieces out. He was a theorist, but this was good for the development of chess theory. Today we say, pawn advances are good if they are supported by the pieces. Quick development and active placement of the pawns (create pawn duos!) play hand in hand.
Classic example game by Fischer how to play if the opp advances his pawns too early and falls back in development: Open files! Doesnt matter if it costs one or two pawns, they will be won back with advantage.