The cake I want to fuck is other girls, and DG is the cake I want to have while I have sex with other cakes.
I think this extended metaphor has gone too far. Essentially I am torn between breaking up with her so I can date/sleep around, and not break up with her because of all the relationshipy things I enjoy. And the latter causes less pain and no feeling of rejection on her part. I kinda wanna suggest a "lets still see each other, but also be free to see others," which is what I was referring to when I said I wanna have my cake and have sex with it too. Normally such a proposition would be result in the same feelings for her as if I were to break up with her, but in this case I can approach the subject as a "what about this option, for what"s best for you?" rather than "you"re not good enough so I wanna bang other girls." I actually have both concerns, but it would be better to approach it with her well-being as the forethought.
@Ham: The backstory, in short, is I"m been living in Korea for 14 months, dating a 31 year old Korean girl for the past 8 or so (I"m 25). The dating prospects were zip back then, but now that I live inside of Seoul I have more options and I understand how to handle Korean women a lot better.
For you, if there is debate between them, that means probably none of them are long term fantastic matches for you. So choose the fun one. Who cares if she"s 19 and crazy.