flying from Barcelona to Pisa (which airline?)

I've flown Iberia a few times and I didn't find anything wrong with it. They are like the Air France regional flights and it will probably be a small jet. I'm not familiar with Vueling though.

I've flown both and they are trustworthy. Just make sure you are aware of their luggage policies, as you won't want to be surprised with any add-on charges/fees that you weren't expecting. Also, I remember when booking with Vueling that we needed to contact our credit card company first so they would allow the charge to go through since it was a foreign transaction.

We flew Barcelona to Rome and I would fly with them again.

We've flown both and never had a problem. Both are based in Spain. Vueling is a younger airline - they began flying in 2004. I consider them both as reliable and trustworthy as any other airline.