I'm not sure why someone who has never been to both Universal and WDW would comment here, but okay.
I though figmentfan423 gave a great list.
Certainly WDW has a special kind of nostalgia, but WOW! HP is very well done! Diagon Alley, especially, looks just like the movie set.
Another difference we have noticed is that the Universal rides are little more intense, the wet rides are more wet, there's a little more spin, and a few are more scary then what you get in the Magic Kingdom. That said, the detail level is very high.
Universal AP's cost less than WDW, especially come renewal time (at least current pricing). Some Universal AP's, depending on which you buy, include relliable park discounts.
Like WDW, Universal offers over 100 places to eat. There's much variety, in flavors and price points. Like WDW, some low cost options are burgers and fried foods. But...overall, I'd say the food is costs and is better quality at Universal. If you want super low cost, Citywalk has a Burger King. If you want quality QS food, at relatively low cost, the new food court at Aventura has an Asian noodle bowl- make your own - that is super. You get to pick exactly your veggies, meat and soup/stir fry. WAY tastier, healthier, and more interesting than what the WDW mods offer, in my opinion. About the only exception: the QS option at the Hard Rock isn't all that great.
Aventura hotel itself is VERY millennial!
Overall, WDW is also very good with special needs dining and food allergies.
If you want a peaceful resort, Sapphire Falls is very nice- though no Express Pass.
If you want EP, I suggest Royal Pacific - lowest price of the deluxes, fun theme, and the courtyard is very pretty with orchids. It is also a relaxing resort. HRH is fun, but very Rock and Roll (not quiet), with a strong perfume smell.