1x7 strand core is a single-strand construction that has one strand of wire rope with seven wires in each strand, formed helically around a strand core - this construction is very stiff.

Compacted strand wire rope is manufactured from strands which have been compacted or reduced in diameter, by passing through a die or rollers, prior to laying the strands into a finished wire rope. The compacting process flattens the surface of the outer wires and re-forms the internal wires of the strand to increase the metallic cross-section area of the strand.
(Conceptually speaking, you can think of the compacting process as squeezing the air out from between the wires that make up a strand.)
This results in both a smoother surface at the strand crowns, and an increase in strength compared to round strand rope of the same diameter and classification.

Compacted strand wire rope is popular with racing sailboats because you can often use a smaller diameter wire while achieving the same strength - saving weight and reducing windage aloft.
Conversely, cruising sailboats can use compacted strand rigging to achieve an extra margin of safety, due to its higher strength, with the same diameter wire.

Compacted strand has also become very popular in the architectural industry for its aesthetic appeal due to its smooth, clean finish and superior luster. You'll see it used in deck and staircase railings, etc.

Increased metal surface area on outer surface and more steel per given diameter compared to conventional round strand rope
Approximately 30% higher breaking load than a conventional wire rope of the same diameter
Up to 25% less stretch than a conventional wire rope of the same diameter
Increased durability and longer service life
Increased areas of contact between the wires for excellent crush resistance
Can be used with mechanical end fittings, and conventional swage fittings using proper technique