you could always kinda mix the two....im flying into london, then flying to dublin, then flying to bruessels, but from there its rail to adam, paris, barcelona before i fly back to london to leave...and once in the city it will be a lot of bussing...so it may be nice to take some rail travel time, but it doesnt mean that is all you can do. the fact that you are only using the rail once though may make it less cost effective. if you r on a tight budget you may want to fly and save your cash and time to explore the different cities and their surrounding areas...but it is of cours your trip, so have fun on whatever you decide!