ChipFlip
Modern minimalism against maximum adjustability, $2.15 apart. The Endgame Gear XM2w 4k sits at $147.84 used, the Mad Catz R.A.T. Pro X3 at $149.99. These represent two opposed ideas about what a gaming mouse should be.
The XM2w is the current formula, executed well
Light, wireless, 4K polling receiver in the box, a shape aimed squarely at the safe middle. Endgame Gear built its following on doing the obvious things properly rather than doing unusual things, and the XM2w is that philosophy in a shell.
Wireless with a 4K receiver at this price is genuinely competitive.
The R.A.T. Pro X3 goes the other direction entirely
Adjustable palm rest, swappable pinky rest, adjustable weight, a modular chassis you can reconfigure to your hand rather than adapting your hand to it. Mad Catz built these for people whose hands don't fit standard shapes.
It's wired, heavier, and looks like industrial equipment. All three are deliberate.
Adjustability has a real cost
Moving parts add weight and failure points. A mouse with a sliding palm rest and swappable panels has more that can loosen, rattle, or break, and on a used unit that's worth checking before you buy. Ask whether the adjustment mechanisms still lock firmly.
The XM2w has nothing to loosen. That's the tradeoff working in the other direction.
Bottom line
Take the XM2w unless you have a specific reason not to. Wireless, lighter, fewer failure points, modern polling. Go with the R.A.T. Pro X3 if standard mouse shapes genuinely don't fit your hand, in which case the adjustability is the whole point and worth the weight penalty.