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

Optimization · Practiced Mastery
Spice economy management and build-order knowledge with modest micro demands.

Optimization · Practiced Mastery
Planning a raid in advance, then executing it where one mistake kills.
Dune 2000 leans Optimization (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.
Dune 2000
Unit micro and build speed matter at competitive pace
Tom Clancy's Rainbow Six
One bullet kills, so entries demand clean aim
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Dune 2000
Human skirmishes add some build-order mind games
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.
Dune 2000
Fog of war hides enemy composition until scouted
Tom Clancy's Rainbow Six
Terrorist placements are unknown until doors open
Same score on optimization - which means the number cannot separate them. The difference is in what each one asks of you.
Dune 2000
Spice economy and build orders decide most games
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.