Definitely take Acela. It's a much more pleasant experience than air travel these days. You'll arrive at Baltimore Penn Station, from which a smart cab driver can get you to the Inner Harbor in 10 mins and skip the Orioles traffic. I don't know that there will be any Os traffic at 9pm; depends on the start time for the game, but the cab driver will know.

Driving distance from BWI is further, about 30 mins, and could be 50 in traffic. There's no great way around the traffic from BWI.