What are the pros and cons of taking the IRS income tax credit vs taking Marketplace premium tax credit?

We've been on a Marketplace plan the last couple of years and have never taken the premium tax credit offered by the Marketplace.  Every year (even prior to enrolling through the Marketplace), we've received a tax refund of roughly $1200.  

We're seeing that we're eligible for a premium tax credit of over $600 / month through the Marketplace.  That comes to over $7200 over the course of the year, so on the surface it would appear that the IRS is offering to either A) Give us $1200 as a tax refund, or B) Give us more than $7200 toward our insurance premiums.  It seems like a no-brainer, which makes me wonder where the catch is.  I'm afraid that if we take the premium tax credit through the Marketplace rather than getting a refund at the end of the year, we'll wind up owing the difference between our usual refund and the premium credits, or roughly $6000.  


Is it true the the IRS is willing to "give" you more if you take it through premium credits?  How can I tell if taking the premium credits won't come back to bite me at the end of the year?