Verdict
Both run modern fast firmware (Bambu A1 at 100-300mm/s, Ender 3 V3 with Klipper at 200-400mm/s). The Ender wins on raw advertised speed, the A1 wins on out-of-box reliability and the AMS Lite ecosystem.
Buy the A1 if: you value time-to-first-print and want multi-color without DIY tinkering. Lower failure rate (4.5% vs ~6-9% on stock Ender 3 V3 firmware) saves real money over 12 months.
Buy the Ender 3 V3 if: you enjoy tuning, want OctoPrint/Klipper customization, or your local market sells Ender 3 V3 50-80% cheaper than Bambu (check used market — Enders flood there).