I think both are places that have their own experience, neither is better than the other.
if you want a unique experience then Komodo Island is the right choice, if you prefer to enjoy the beauty of the sea, especially underwater beauty then Gili Island is a more appropriate choice.
but this does not mean that Komodo Island does not have tropical natural beauty, in my opinion both are very beautiful and very very romantic places and most importantly both have local residents who are very hospitable to all tourists who visit no matter where the tourists come from.