sell the 27 yr old.
For one, the 27 yr old will last shorter then the 25 yr old. 2 more seasons is valuable in BB. For two, the first center would be a true center. the second center could possibly play PF but still, the second center has better secondaries and thus you'll get more bang for the buck.
3 Time NBBA Champion. Certified Trainer. Mentor. Have any questions? Feel free to shoot me a BB-Mail!