head to head
Tom Clancy's Rainbow Six asks more than Grand Theft Auto V, and the gap is optimization.

Execution · Practiced Mastery
Sandbox crime playground spanning shooting, driving, and a persistent online economy.

Optimization · Practiced Mastery
Planning a raid in advance, then executing it where one mistake kills.
Grand Theft Auto V leans Execution (Practiced Mastery); Tom Clancy's Rainbow Six leans Optimization (Practiced Mastery).
Tom Clancy's Rainbow Six leans a little harder on execution, though the gap is small.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Tom Clancy's Rainbow Six
One bullet kills, so entries demand clean aim
Tom Clancy's Rainbow Six leans a little harder on reads, though the gap is small.
Grand Theft Auto V
Online PvP exists but mostly gear/positioning, not modeling.
Tom Clancy's Rainbow Six
Multiplayer raids add human counterplay
Tom Clancy's Rainbow Six leans a little harder on variance, though the gap is small.
Grand Theft Auto V
Some mission and lobby randomness.
Tom Clancy's Rainbow Six
Terrorist placements are unknown until doors open
Tom Clancy's Rainbow Six leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Tom Clancy's Rainbow Six
The pre-mission planning phase is the real game
A matching score does not mean a matching test. Two games can both sit at 10 on execution and demand completely different things of you - which is why the reasoning above matters more than the number beside it.