Depends, both story are unique. You can have romance scenes to both but if you want to betray Galiano and goes for Garth then go for it. Galiano is a lesser evil type of character with actual kind and good tragic past, albeit Garth is more like a morally good type character wherein history of his ancestors are condemn to death because of Garth's race were insipid supremacist. They were equally good for me. But in terms of financial things? Depending on many factors (like if you are a man or a woman, respectability, and also your sexual preference). There is someone in this page who actual made Galiano a whore and repeatedly milking him money (character:is top/man). Whereas you can only blackmail Garth on the other hand, if you choose him and he'll pay you hefty, hence, milking him too. (Note: Garth's money giving is a one time event wherein he'll buy your loyalty like an auction to him).
Note: sex scenes have variation with Galiano, the only sex scene I know with Garth was giving him head. (Partly due to my character is woman, and have sex parts relating to that.)