Casio G-Shock GA2100-1A1 vs Casio G-Shock GA-B2100

Both are the same 48.5 × 45.4 mm carbon-cased 2100 Series watch, so the fit on the wrist is nearly identical. The GA-B2100-1A is the better buy for most people: Tough Solar removes the battery swap, Bluetooth adds phone-based time sync and step tracking, and the Super Illuminator double LED is far brighter than the single LED on the GA2100-1A1. The GA2100-1A1 is the leaner, simpler pick: no app, no charging worries, and the same shock resistance and 200-meter water resistance. Owners of both praise the slim case and light weight; the common complaint about the base model is the dim light and the battery service every few years.

• Choose the GA2100-1A1 if you want the simplest version of the 2100 case with no app pairing, no solar charging and nothing to set up.
• Choose the GA-B2100-1A if you want solar charging, Bluetooth time sync and a genuinely bright backlight in the same slim carbon case.