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.

Execution · Competitive PvP
Arcade punch timing with counter prediction in human bouts.

Execution · Pure Mechanics
Console shooter execution across scripted set pieces and once-massive human multiplayer.
Ready 2 Rumble Boxing leans Execution (Competitive PvP); Resistance 2 leans Execution (Pure Mechanics).
Resistance 2 leans a little harder on execution, though the gap is small.
Ready 2 Rumble Boxing
Punch timing, dodges and rumble combos reward quick hands
Resistance 2
Weapon handling and boss dodging demand console-shooter precision
Same score on reads - which means the number cannot separate them. The difference is in what each one asks of you.
Ready 2 Rumble Boxing
Human bouts become feint-and-counter prediction
Resistance 2
60-player multiplayer rewarded reading humans; campaign Chimera don't adapt
Same score on variance - which means the number cannot separate them. The difference is in what each one asks of you.
Ready 2 Rumble Boxing
Nothing hidden once boxers are learned
Resistance 2
Campaign encounters are set pieces
Resistance 2 leans a little harder on optimization, though the gap is small.
Ready 2 Rumble Boxing
Boxer matchups and rumble meter use are quickly mapped
Resistance 2
Exotic weapon choice and class co-op roles add planning
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.