Submitting to Journal: General prestige Versus Localized Focus
Since there is no guarantee that your paper will be accepted, my suggestion would be to submit to the more prestigious one first, imagining that it is harder to get accepted there. You can always submit to the other later if you are disappointed in the first. 

Also, be aware that this is only your first (or early) work, and that you will have opportunity to publish again later, perhaps in the more arcane corners that fit your field best. But a wider reputation is probably best for a new academic. 

But your advisor is correct. It is a bit of a personal choice and if you get it "wrong" it won't end your career.