Quick answer
Do not overthink Suica vs Pasmo.
Both cards are accepted on most trains, subways, buses, convenience stores, vending machines, and local transit systems across Japan. For a tourist, the brand almost never changes the fare.
Arriving at a JR East station? Regular Suica is simple if available.
Staying less than 28 days? Welcome Suica or Pasmo Passport can be convenient if you do not care about refunds.
Want to keep the card? Regular Suica or regular Pasmo is better than tourist-only cards.