It favors the people who like to sleep late. And it disadvantages the people who do rope drop, as a big chunk of that advantage is disappearing. It used to be that you could do a lot of rides if you arrived at RD and gathered fastpasses, even after they stopped taking late FPs. Now it appears that 3 will likely be the limit regardless, and with FP returns starting at 9 AM it's unclear if morning standby lines will stay short or start backing up much sooner.
Additionally the new system disadvantages the people who aren't tech-savvy or don't carry smart phones. And those with poor battery performance.
I don't believe there was an advantage or disadvantage with the old FP system for resort vs. non-resort guests, nor do I believe there will be once the new system gets up and running fully. Unless you count having Stacy remind you incessantly on resort TV to get your FPs. I actually will be quite interested to see if they have Stacy hyping FP+ on resort TV once this gets up and going. By the time folks arrive onsite all the headliner spots could easily be gone, and it's probably too late to get one. At least that's what I think. YMMV.