as far as i am concerned ,the most comfortable is trip by plane ,but as you konw ,it costs the most .if you are not in a hurry you can take a train or if possible you can trip by sea,it is not expensive and you can appreciate the sights .
Oh.As a business ,you want to visit what place you want to go to .I suggest that you had better take a train or a bus so that you can see the beautiful scenery on the way .you will forget be tired and you feel comfortable and happy on the train or the bus .and it cost low.离题了