I prefer the train, but a combination of train and a few flights usually works best in terms of both cost and convenience. Since you prefer a very flexible travel style, I’d recommend the train for the majority of your travels. Flights require committing to exact locations, dates and times in advance — usually well in advance to take advantage of the lowest fares. Train tickets are also cheaper if you commit to exact date and time in advance, but you can always pay regular fare and just buy a ticket and hop on the train — or buy a railpass before you leave home and use that as your ticket to travel to wherever-the-mood-leads-you-today.