Yes they are friendlier and don't usually drop-out if you wipe. They can get a little bossy at higher levels but they're not condescending, in my experience.
Edit: If you play with Japanese and have never run that particular dungeon, please watch a youtube video before entering (especially if you're a tank--the leader) since it will be a bit more difficult for them to communicate with you and vice-versa.
I'd love to see this topic die out, but wanted to comment on this atleast. This isnt actually remotely true.
First, how friendly they are completely depends on the player itself. Are there less trolls in the JP community in general opposed to the NA community? Sure, social standard and image may have them refrain from such things a little more than other players. But they're every bit as friendly or unfriendly as your casual encounter in the city or on the fields. It's irrelevant really.
Second, while they are infact less inclined to explode in your face and cuss you out for above mentioned reasons, they will not tollerate a lot of mistakes and will kick you out or give up an entire run just to get you out of the group. Also, while they might not say so to your face, they will (and do) complain to their Free Company and/or Linkshells about you to the point where everyone in it will make sure not to ever invite you ever again. Or simply in party chat in japanese. Especially if they dont know you can read it. They can be pretty brutal.