Let's pit those two 6th-level monks against level-appropriate challenges, such as an average xorn. Xorns take half damage from slashing weapons, so the monks won't use their kamas.
Dextrous monk: hp 36, AC 16, AB +6/+3, damage d8+2 (bare hand).
Strong monk: hp 36, AC 15, AB +7/+4, damage d8+3...