head to head
Neither is meaningfully harder - they pose close to the same test. The widest gap is reads, and it is a single point.

Execution · Practiced Mastery
A cover-based shooter where precise aim and positioning against human or AI opponents dominates.

Execution · Competitive PvP
Tactical gunfights testing aim, entry planning and prediction of human opponents online.
Gears of War 4 leans Execution (Practiced Mastery); Tom Clancy's Rainbow Six: Vegas leans Execution (Competitive PvP).
Same score on execution - which means the number cannot separate them. The difference is in what each one asks of you.
Gears of War 4
aim and cover timing decide fights
Tom Clancy's Rainbow Six: Vegas
Aim and snap-to-cover gunplay punish slow hands
Tom Clancy's Rainbow Six: Vegas leans a little harder on reads, though the gap is small.
Gears of War 4
predicting human opponents in PvP
Tom Clancy's Rainbow Six: Vegas
Multiplayer angles and pushes demand reading human opponents
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Gears of War 4
weapon spawns and drops vary
Tom Clancy's Rainbow Six: Vegas
Terrorist hunt spawns vary modestly between runs
Gears of War 4 leans a little harder on optimization, though the gap is small.
Gears of War 4
cover positioning and loadouts solvable
Tom Clancy's Rainbow Six: Vegas
Room-entry planning and map knowledge are studyable
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.