head to head
Tom Clancy's Rainbow Six: Vegas 2 asks more than Grand Theft Auto V, and the gap is execution.

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

Execution · Practiced Mastery
A cover-shooter Rainbow Six blending tactical room-clearing with solid gunplay.
Grand Theft Auto V leans Execution (Practiced Mastery); Tom Clancy's Rainbow Six: Vegas 2 leans Execution (Practiced Mastery).
Tom Clancy's Rainbow Six: Vegas 2 leans clearly harder on execution.
Grand Theft Auto V
Driving and shooting demand decent inputs.
Tom Clancy's Rainbow Six: Vegas 2
Cover-based gunfights still punish poor aim
Tom Clancy's Rainbow Six: Vegas 2 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: Vegas 2
Multiplayer brings some human adaptation; AI is scripted
Tom Clancy's Rainbow Six: Vegas 2 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: Vegas 2
Enemy placements partially unknown per encounter
Tom Clancy's Rainbow Six: Vegas 2 leans clearly harder on optimization.
Grand Theft Auto V
Heists, money loops, builds learnable.
Tom Clancy's Rainbow Six: Vegas 2
Room-clearing order and squad commands are solvable tactics
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.