1440p Game Benchmarks
The following charts cover 2560x1440:
For Honor
Grand Theft Auto V
Mafia 3
Sniper Elite 4
Watch Dogs 2
The Witcher 3
All of the factory-overclocked cards offer similar performance, more or less. Apparently, these cards already operate so far above their sweet spot that performance no longer scales linearly with clock rate, and thus the price for even a slightly higher frame rate is a disproportionate increase in power consumption. Thus, to find the "best" Radeon RX 480 for your purposes, compare power and cooling, rather than the gaming results. Especially for the RX 480, a more modest approach pays off.
MORE: Best Graphics Cards
MORE: Desktop GPU Performance Hierarchy Table
MORE: All Graphics Content