I feel as though it is important to clarify my bias before I continue with this argument. I am(pause for dramatic effect) a Bubbler addict (oh no!) and much prefer them over monsters, and here is why. 

Starting off, these drinks are both classified as energy drinks, and therefore are not good for you.  

But even with this, Bubbler it is much better for you. I went into every ingredient in both Bubbler and Monster and was shocked with my findings. Monster contains high amounts of lab formulated chemicals such as sucralose which causes liver inflammation. Or Panax ginseng extract which has hypolipidemic potential. 

Not to say Bubbler does not have bad things. The dose-response relation between a low energy bulking sweetener, erythritol, and the induction of diarrhea symptoms was investigated in healthy human subjects. 

So in my opinion I think Bubbler won for health, with only one debatable ingredient, but what are you looking for in an energy drink? If we look at Monster we find chemical edjunered caffeine, but it does get the job done. However, it tends to wear off a lot faster. Verses Bubbler and all its natural caffeine, which lasts longer in the body. We are looking at 86 mg vs. 69 mg of caffeine, so for this one I am going to call a tie. 

For overall flavor I think there is one possible answer. I believe it is Bubbler. This one there is no scientific way to back it up. In conclusion, I think there are so many energy drink options, but you should probably eat, sleep, and then reach for the drink.