Airlines

American, Delta, Level, Norwegian Air Shuttle and United for Barcelona.
Iberia, Norwegian Air Shuttle and United for Madrid.
I'm talking non-stops.
You can Wikipedia any airport and an updated list of all non-stop flights is listed.

Start at this site, clicking on the "Multi-city" tab and see what shows up.
https://matrix.itasoftware.com/

Just do a search on kayak.com

Whoever has the best fare. The process sucks about the same on all unless spending the $$ for business or first class.

I agree go with whatever non stop you can afford.

Hey
I'm looking at flights in November from Florida (Orlando preferably). Looks like roundtrip is less costly, and that too with Barcelona as the destination. I don't know whether to trust this Norwegian Shuttle or whatever, but they have the best rates. Also most of their flights have gatwick airport in London as a stop, so also unsure whether 2 hours in London will be enough for flight change.

Also most of their flights have gatwick airport in London as a stop, so also unsure whether 2 hours in London will be enough for flight change.

I wouldn't want to risk it, that's very tight.

I know that direct flights are more expensive but it's a cost that I'm prepared to absorb having experienced non direct flights.