We discussed this when they first announced the addition of 30 minutes early entry for resort guests:
The Touring Plans crew has estimated that the extra 30 minutes in the morning could save you at least an hour in line for the same set of attractions vs someone staying offsite without this benefit.
If you’re not the type to rope drop, the only other benefit is internal transportation / skip TTC. Also walking distance if you stay at certain deluxe hotels. Lastly, there’s the magic of being in the Disney bubble.