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!