For most new scuba divers, a medium-soft paddle fin is the better first purchase because it builds useful kicking control and works across more dive conditions. Split fins are the better pick when low-effort cruising and reduced leg strain matter more than precise power in current.
For most recreational divers doing repeated dives at moderate depths, nitrox is the better choice after proper certification because it reduces nitrogen loading. Air remains the better gas for deeper dives, simple one-off dives, and sites where nitrox is unavailable or costly.
For most recreational divers taking warm-water dive trips, a lightweight jacket BCD is the easier travel choice because it packs as one familiar unit and needs less setup. An aluminum backplate and wing wins for divers who want a modular system, consistently good trim, and a configuration they can tune for different diving.