HUTB numbers can be checked on the government website.
https://empresa.extranet.gencat.cat/rtcwebguies/AppJava/cercaEstabliments.do?pst=5&lg=
in the 'Identificador registral ' section type in HUTB-###### . # indicates a number. There should be 6. I had to try a few combinations, but my apartment came up.
Regardless of company providing service, you should double check the HUTB number. There is no guarantee that the other companies that represent rental hosts are any more vigilant than AirBnB. The information is only as accurate as the host is honest, IMO.
VEO is a spanish short let rental company that operates in a few cities including Barcelona. Friends have used them in Sevilla.
The reason I like AirBnB is that they hold the security deposit against your credit card so I don't have to hand over hundres of euro in cash and hope that I get it back - then what to do with all those Euros? Also, AirBnB holds payment to the host until 24 hours after check in so that if you don't have what you were sold, or if there are issues, they are the intermediaries and you don't have to try and retrieve money from an individual. This to me is peace of mind and better value for my dollar.
There is a lot of fine print in apartment rentals and Booking, VRBO, in country companies all have different payment methods, payment times, deposit amounts and methods to pay security deposits. Ensure you know the process (as it may be different for each lodging) and that it suits you.