Is it better to take a train or fly from Frankfurt to Berlin?

It depends 100% on what is "better" to you.

It is a little over an hour to fly from FRA to TXL and it is between 4.5 - 5 hours to take the train.

Air Berlin flies from FRA to TXL for about $150US.

The train costs about $70US for a Sparpreis and about $110-150US for a full-fare ticket.

Which option is "best" for you?

The one hour flight will take at least 3 and possibly 4 disjointed hours of train to airport, check-in with all the airport security hassle, a cramped flight then another train or bus the last leg into Berlin.

The flight isn't an experience, and won't show you anything of Germany or give you a chance to relax. But it may save a few minutes.

The train is direct, centre to centre from 29 euros ($35) booked at German Railways www.bahn.de/en

These are superb 175mph InterCity Express (ICE) trains.

You can use the bistro-restaurant car (where food is served on real china, with metal cutlery, no airline plastic here) or read or simply relax and watch the scenery - it's chill-out time. All seats have power sockets and there may be wifi. Feel free to bring your own picnic and even beer or wine.

I'd probably pick the train UNLESS you are:

1. Collecting FF miles
2. Landing in FRA and looking to immediately head to Berlin

I generally take a train rather than fly. It's generally cheaper, more comfortable, and more convenient.