I don't trust buses and there is an actual cost factor (fare, taxi, parking) which can be counterproductive if you're trying to save money on a flight. It's still a two hour ride which is a "self imposed layover" in a bus or train and that doesn't include arriving at the PTC 15 to 30 minutes prior to departure in addition to potential Boston traffic issues which has caused me to miss a flight in the past. I'm already at my one stop layover before you even arrive at Logan and you are still an hour away from boarding your plane! Flying out of Portland is convenient, a bus or train ride to Boston is not. There is no right or wrong Jeff and it's whatever works best for you.