Padraic, for Andamans, you will get away with either reel. As Leo said, the 14000 has the benefit of being noticeably lighter. Conversely, the bigger reel is more robust. With the previous generation Stellas, I found the ongoing rigors of GT fishing to be simply too much for the 10000s and they found themselves continuously going back and forth to Shimano's service centre.
In more recent years, fishing areas like New Caledonia and outer reef locations like Ashmore or Osprey Reef have found even the 18000s wanting in line capacity against really big GTs and dogtooth. I don't even bother with the 14000 anymore. It is like having a popgun at a gun fight.
It really comes down to what you feel you want. My suggestion? Go the 18000