Ruger-57 5.7x28mm vs Smith & Wesson M&P 5.7 5.7x28mm

Both are full-size 5.7x28mm pistols with factory optic cuts and two magazines, and their barrels are within 0.06" of each other (4.94" vs 5.0"). The Ruger-57 5.7x28mm is the lighter gun by 2.2 oz (24.5 oz vs 26.7 oz) and $150 cheaper at $549 against $699, but the Smith & Wesson M&P 5.7 5.7x28mm is the smaller one on every linear dimension — 8.5" long, 5.25" tall and 1.1" wide against 8.65", 5.6" and 1.2" — and it holds 22 rounds to the Ruger's 20. The M&P's single-action trigger is listed 1.2 lb lighter (3.4 lb vs 4.6 lb), and its gas-operated Tempo barrel ships threaded where the Ruger's does not.

Pick the Ruger-57 if:

• You want to spend $150 less ($549 vs $699)
• You want the lighter pistol at 24.5 oz, 2.2 oz under the M&P
• You want a fiber optic front with an adjustable rear, and an ambidextrous manual safety

Pick the Smith & Wesson M&P 5.7 if:

• You want 22+1 instead of 20+1
• You want the lighter trigger: 3.4 lb single action against 4.6 lb
• You want a factory threaded barrel, a published 7.13" sight radius and a stainless slide

Both are optic-ready 5.7s with ambidextrous safeties, within 0.15" of each other in overall length, so neither is meaningfully easier to carry. The choice comes down to $150, two rounds and 1.2 lb of trigger weight against 2.2 oz of carry weight.