Glock G21 Gen5 MOS .45 ACP vs Smith & Wesson M&P 45 M2.0 .45 ACP

Both pistols sit within 0.8 oz of each other and run polymer-framed striker-fired actions, so the spec table reads close — except in two places that matter. The Glock G21 Gen5 MOS carries 13+1 to the M&P 45 M2.0's 10+1, a 3-round gap that is the largest capacity difference in the .45 ACP polymer class. The G21 is also factory MOS-cut for direct-mount optics with adapter plates and ships with three magazines. The M&P 45 M2.0 has no optic cut at all in .45 ACP and ships with two magazines, but offers four interchangeable palmswell inserts versus the Glock's backstrap system.

Pick the Glock G21 Gen5 MOS if:

• You want 13+1 .45 ACP capacity — 3 more rounds than the M&P 45 in the same size class
• You want a factory optic cut and ship-with adapter plates, since no .45 ACP M&P M2.0 variant offers an optic-ready slide
• You want the largest pistol aftermarket on the market — more holsters, sights, and replacement parts than any competitor

Pick the Smith & Wesson M&P 45 M2.0 if:

• You want four interchangeable palmswell inserts that adjust grip circumference, not just the backstrap profile that Glock's backstrap system changes
• You want the option of a frame-mounted manual thumb safety — Smith & Wesson catalogs an ambidextrous safety variant of this M2.0, while no factory G21 ships with one
• You want the 18-degree grip angle that owners coming off 1911s typically prefer over Glock's steeper 22-degree angle

Both run polymer frames, both ship with Picatinny rails for weapon lights, both share the same 4.6" barrel length within a tenth of an inch, and both are striker-fired with a trigger safety. The decision is capacity and optic-readiness versus grip customization and grip angle.