Airline connections are about risk tolerance. Airlines will only sell connections they believe they can make the majority of the time. Since it's the airlines' responsibility to get customers to their destination when there is a misconnect, they try to avoid problems.
Aside from the terminal change issue that other people have discussed, I see three other things to consider.
1. Travel Party: If your group is one or two people who don't have a problem power-walking (if necessary), a 42-minute connection might be okay. However, if your group has younger kids or anyone needing assistance, it's not a smart decision.
2. Time of Day: Generally speaking, the first few flights of the day tend to be a little more reliable than afternoon or evening flights. There's less of a chance of a delay simply because the airplane leaving Grand Rapids in the pre-dawn hours almost certainly arrived the night prior. Personally, I'd rank a 42-minute connection in the early morning a much safer bet than the same connection time in the evening.
3. Schedule: Most importantly, you'll want to think about what might happen if you do miss your connecting flight. A big airline like American will provide plenty of later flights to get you to Orlando. I picked a random day, but it appears the flight schedule matches:
If you miss your flight, you'll almost certainly get placed on one of the 5 other nonstop flight. The legacy airlines (American, Delta, United) have invested in technology that automatically rebooks people who misconnect. Chances are strong that if you have a delay, all you need to do is check your phone/email/mobile app when you arrive in Philadelphia and you'll have been rebooked.
Note: Technology is not perfect. If you don't like the auto-rebooking, simply go to one of the customer service desks or call America. Also, same-day rebooking generally means larger parties are not seated together. If you absolutely need to sit together or any reason, ignore all of this and book the longer connection.
