Answer:
You are better off to take the bus. It's a smooth ride, costs $4 for the express bus, and at the Panama City bus station, there are plenty of taxis to take you to Tocumen Airport. The cost for the taxi will be about $25. If you are flying out of the Albrook Airport (the one for Panama travel), you will already be there. The bus station is part of the airport. My husband and I caught a ride from Colon to Panama City with someone who was going there anyway, and it was $50. A taxi would be more.