(A) Denver (Airport Code DEN): 

1 hour and 45 minute drive.   

Denver is typically the least expensive airport to get into.   However, it will take 30 to 45 minutes to get to the rental car terminals.  

Take I-70 to route 9.   At the top of Loveland pass, you will go through the Eisenhower Tunnel at an elevation of 11,992 feet.  It is the highest mountain pass, in the world, that regularly stays open during the snowy winter season.  Colorodo DOT does their best to keep the pass operable in the winter - but it can be a challenge with the snow.  Just be aware of this as you are departing Breck - trying to catch a flight out of Denver Int.

(C) Colorado Springs (Airport code COS):   2 hour and 30 minute drive.  

It is a far smaller airport so rental car pick up is a breeze and the drive is very pretty.  Going up little less stressful.   If you have never been - a drive through "Garden of The God's is a free easy and scenic way to get to route 24 that will wind you up an through Manitou Springs.  Just after Hartsel, catch  Highway 9 and be on your final approach to Breck (remember to drive slowly through Fairplay and Alma unless you like contributing to the local city budget via speeding tickets.)  After Alma, you will go over Hossier's Pass (11,532).  It is not nearly as well traveled as Loveland Pass - so in the winter it can be a challenge.  The views are very pretty.

(D) Eagle Vail (Airport Code EGE): 45 minute drive.  

There are far fewer direct flights - and typically costs more than the other two airports.  Here, you will be going over Vail pass - typically not a big deal.