If you're coming from Key Biscayne go for the Berrys. The Abacos are fine if you like Miami
A little bit in jest but the Abacos, unless you go to the far north cays is a bit too busy. Most first timers end up stuck in the Hub area (Marsh Harbour, Hopetown) and don't get north of Whale Cay Cut. The Berrys offer a lot more if you prefer boat life to shoreside amenities. Better fishing, better snorkeling, nicer secluded anchorages. As long as you have enough provisions and water stay in the Berrys. If you need to re-supply often go to the Abacos. They're both nice but my choice would be the Berrys. If you prefer eating out and bars the Abacos would be the spot.