Fly or train to Seville from Barcelona?

It depends on the cost but I would probably fly because:
The train takes 5 hours or more not counting the time you would take to get from the airport hotel to Barcelona Train Station.
Taking the train requires you to be vigilant for the duration of the trip as it makes stops people getting on and off.

The flight takes 1 hour 30 minutes not counting the time you need to get to the airport from the hotel and go through security.
The good point is that the train arrives in Sevilla in the center of town
The airplane requires you to get to the center of town if you are not staying by the airport but it is not far.

See lost luggage via Veuling post on BCN to Seville. You might want to check carry on restrictions and consider not checking a bag.
Other than luggage risk, I would fly.

I took bus all over Spain. One 8 hour bus ride that was through the night, someone stole our hats. Our bags were safely wrapped around our legs, but the hats were sitting in the open. The thieves ended up with an extra large males hat (which they don't have heads that big out there), and an extra small female at (the size of a 6 year olds head)... so jokes on them.

Flights are so cheap and fast, they are easy to do out there. I was circling Spain stoping in all the major cities, so bus was ideal for us. It is a lot cheaper to go by bus though. I was on a budget ;)

We are flying from Barcelona to Granada as it is much faster than train. Had we gone to Seville first instead of Granada first, we would have flown also.

I think our ticket was about $100. Worth it to save so much time.

We flew from Barcelona to Granada last week and would fly to Seville if faced with that option. Also had a lovely experience at Overland Suites Catedral if you are still looking for accommodations.

I flew from Barcelona to Sevilla on Vueling and the charge was only about $49. I booked in January for a May flight. Less expensive and less total travel time (and as I recall, better time-of-day) than other public transit.

Have a wonderful time!

Flying is quicker but when you take into account getting to the airport then having to be there 2 hours before departure 1hr 30 flight then transfer to city centre in Seville the 5 hour train may be a better option and it goes from centre to centre.

Let me clarify the trains. If you take the train from Barcelona to Seville it is 5 hours? Do you go through Madrid on AVE? We then to tour the area via bus? We plan to also stay in Tarifa and visit Granada and maybe Cordoba. We also want to visit Morocco and Gibralter.

The flight is faster but not by as much as you think. If you stay by the airport then you leave your hote 2 hours before the flight, fly for 1.5, then get a cab to your hotel in the center. 4 hours.
The train takes 5 hours plus transit to and from the station. So 5.5 - 6 hours total

A 2 hour difference may not be enough to make your decision. It's a judgement and preference call at this length.
I'd go train because flights get delayed easier, I hate airports and flying, and I like that I can get up, walk and see some scenery from the train. If I were checking luggage this would be even more in favor of train - lost luggage and waiting at baggage claim are hassles I don't want. For me in general for any trip less than 6 hours by train I prefer train. Over 6 and direct flight available I choose the flight.

I thought about this too when planning how to go from Barcelona to Granada or Sevilla. I decided to go to Granada first and then bus to Sevilla. From Barcelona, I decided to fly. Took me five minutes to make that decision as soon as I saw the duration of travel for bus and train. I also decided I would take the first flight out to minimize delays, but after checking the arrival times for past flights, I found that Vueling was usually about 15 -30 min behind. Someone who lives out there told me that Vueling had to get their act together due to problems last year and that those issues are not expected this year. So far it looks good. If you book flight in advance you can expect 38-58 Euros per ticket.

see my post on my Spain itinerary... jlkwinone

We took the train from Barcelona to Sevilla. Our family of 6 adults. It was the most relaxing ride on the high speed AVE train.

The countryside was beautiful and it only made a few stops. 5 1/2 hours total relaxation...no rush. we upgraded our seats and booked on line from the US. I fly all the time for business so this was a nice change of pace.

Stay overnight close to BCN Airport.
Two choices ...
https://m.nh-hotels.com/hotel/nh-collection-barcelona-tower/
http://www.hotelciutatdelprat.com/en

Book Vueling VY2252 on the 2nd, departing at 10:05, arriving Seville at 11:50.