These are two of the best theme parks on the planet, built for different moods and different trips. There isn't really a “better” one — the right choice depends on your itinerary, not a ranking. Read the comparison below, then check which one actually fits the trip you're building.
Which One Actually Fits Your Trip
Before You Go
Buy tickets online in advance for both parks. Walk-up tickets exist but sell out on busy dates, and online booking is usually cheaper than at the gate.
Both parks use a virtual queue / paid express system (Disney Premier Access, USJ Express Pass) — for popular rides like Super Nintendo World's Mario Kart, an Express Pass is close to essential on weekends and holidays.
Neither park is a true day trip from the other city — Disney is Tokyo-only, USJ is Osaka-only. Don't plan on doing both in the same 2-day window unless you're taking the Shinkansen specifically for it.
If you're doing both parks across your trip, buy tickets for each separately — there's no combined pass between Disney and Universal.