A note before you act: entry and transport policies can change. Recheck the official source relevant to your nationality and route before departure.
Compare door-to-door time
Rail often works well between cities with central stations, while flights can make sense across much longer distances. Include the trip from your hotel, security procedures, waiting time and arrival transfer in every comparison.
Protect the important connections
Avoid building a fragile chain of separate tickets before an international departure or a fixed event. An extra night near the final gateway is often more valuable than squeezing in one more stop.
Plan luggage as part of the route
Frequent changes feel very different with large suitcases. Pack for the route you designed, confirm each carrier's current allowance and consider leaving nonessential items at a longer-stay hotel when practical.