Aside from the eight on-site resorts being impeccably well-themed, each one provides complimentary transportation to the park via shuttle, boat, or walking path.
Staying off-site means having to deal with expensive ride-shares or parking prices.
On-site resorts also grant you access to a private security entrance and one hour of early park admission, ensuring you're able to ride your favorite attractions before the masses arrive.
The three premier resorts also come with the added bonus of complimentary Universal Express Unlimited passes that let you skip the regular lines at some attractions.
Express Passes are available to purchase on their own, but it's almost always cheaper to pay for a resort that includes them than to purchase them outright with other lodgings.