Barcelona El Prat taxi
 

Going from Barcelona El Prat airport to Terrassa: Hotel advised us to just take a taxi at the airport. Is it better to book one in advance?
It's for 2 people, handluggage only.
Thanks for any advice, since I have not been there in ages!

There's a well populated taxi rank at the airport so no need to book in advance.

If all you have is hand luggage you could take the airport bus or train and metro. See Rome2Rio.com.

I need to get to Terrassa; by train/bus it's 1,5 hours, taxi only half an hour.
I'll just get a taxi on arrival then.

Rome2Rio says it's 24 minutes by train and metro and 34 minutes by bus.

That's weird, thursdaysd, my rome2rio says Airport to Terrassa is 1h9 minutes by train (with one transfer), 1h35 by train/metro/bus.
35 mins taxi.

Sorry, I misread your post as Terrassa Hotel in Barcelona! Given the price difference I would take the train, but I rarely take taxis in Europe.