Originally Posted by abraxis

There's practically no difference in how they're accepted in typical use. You can use both on buses, subways and JR (excluding Nozomi). I was recently in Kansai and recharged and used my Suica in Kyoto and Osaka. It's great that all the different variants of Suica (issued by the different JR branches) work with each other and all over.

The difference between Suica and Pasmo is if you're a commuter and which company issues your commuter pass. JR or Eidan/Toei.

As a tourist, pick which ever one you fancy. I use a Tokyo Monorail Suica with a green monorail car on it. Twee!