LoanDepot Park must be great when it's filled to capacity. We went years ago to a game in September, hoping to see the Nats clinch the division (they ended up doing it a few days prior). It was interesting but nothing really special.
We caught a Nats-Rays game this season at Tropicana. Despite its age, it was actually a really fun experience. The home crowd was really into the game, unlike in Miami. The only odd thing: we bought parking in advance at one of the lots directly next to the ballpark, but when we got there a little late during the 2nd inning, there was no attendant to be found. Nobody to scan our ticket upon leaving either. I noticed you could also pay with ParkMobile.