I'd say go with the Boeing type. Take advantage of the opportunity to learn the FMC and MCP. I've flown both (75/76 and A320) for over 2,000 hours. Seems like there are more Boeings (73, 74, 75, 76, 777, 78, etc) with attainable flying at a fairly junior seniority. Let the airlines put you through the Airbus type if/when the opportunity presents itself.