The advantages of the Los Angeles Lakers signing DeMarcus Cousins:
Three-point shooting
This is the biggest advantage that DeMarcus Cousins has over Hassan Whiteside. While Cousins is not shooting the three-point ball at an exceptionally high percentage, he does offer the floor-spacing prowess that Whiteside absolutely does not.
This is more important while Anthony Davis is out. While Davis is not a prolific three-point shooter, he can stretch the floor and having him as a threat outside of the paint really helps the team’s floor spacing. Cousins could provide a similar impact.
Cousins has made 39 of 116 attempts this season (33.6%). Whiteside has attempted 26 threes in his entire career.
Familiarity
DeMarcus Cousins spent most of last season with the Los Angeles Lakers. Even if he does not play, he has a general idea of the schemes and style of basketball that the Lakers play and also already has a relationship with LeBron James, Anthony Davis and co.
That same familiarity is not present with Whiteside, thus the transition to the new team might take slightly more time to completely form. Plus, there is always the slim chance of him not meshing well with the locker room.
More versatile (thus better) defense
You might think that Hassan Whiteside is the better defensive player if you just looked at the box score but that is not the case. Whiteside is good at what he does, but what he does is rather limited whereas Cousins is someone who can also defend near the rim but can do more defensively as well.
The advanced metrics paint a better picture. Cousins has posted a 1.9 Defensive Box Plus/Minus this season, whereas Whiteside has posted a -0.1 DPBM. Whiteside is right around average, Cousins is above average. Since 2016, Cousins has a 2.1 DPBM, Whitside has a 0.8.
Cousins ranks eighth among centers with at least 300 minutes played this season, Whiteside ranks 26th — out of 39.