I was initially in favor of Catalunya having the decision to choose which way they want to go, however after reading more into it, and looking at the Pro-Independence parties program and how they actually plan to tackle an independent Catalunya(They have absolutely no working plan), I'd have to say it would be better for them to stay with Spain.
However, in order to keep this from getting out of hand, the Spanish Government and the puppet King should shut the fuck up and work towards an agreement on, a deal on autonomy with Catalunya. They had a revised deal granting them greater fiscal powers similar to that of the Basque Country, but that was scrapped the moment PP stepped into government, and that's when the independence movement truly kicked off.
You cannot demand independence and have no plan on how you're going to make everything work(institutions, economy, trade deals, border control, etc) unless you want to end up like Venezuela or a Banana republic.
Emotionally driven decisions never end up well.