The Fantom G7 has Roland’s PHA-II keybed where the Juno DS 88 has their Ivory Feel G keybed.
I have no idea as to the difference in feel but the G7 keybed is now at the PHA-4 iteration and this is available in the new RD88 piano or FA08 workstation, the PHA-4 includes an escarpment feature but I am unsure if the DS G keybed has this feature.
You're thinking of the G8. The G7 is not a hammer action board.
As for the original question, I'm hard-pressed to find any reason to prefer a Juno DS except for price and travel weight. Like-size-to-like-size, the Fantom will have the better action, and I think it will also have the better sound set (most of the DS consisting largely of a subset of Fantom sounds), and it's far more fully featured overall (though there may still be some functions that are easier to do on the Juno). But it gets tricker if you were looking at the DS88, which does have a hammer action where the Fantom G7 does not, and you might prefer that.