On the bottom of either list, life will probably be similar. The destinations may be 73 one month, and airbus the next so it's hard to say which would be better flying. I've been gone from MIA for a few years now, but 73 MIA was a great time, right up until they combined the domestic and international divisions.
I wouldn't listen to the anti-Boeing crowd, I've flown both. The bus is more comfortable, no argument there, but I like pretty much everything else about the 73 better. If my seniority stays about equal, and the trips are about the same, I plan on staying on the 73 until I can hold a wide body CA seat.