So really... what is ADV 4? Here are the facts:
Set Size: 132 in Japan, ??? in the US
The Japanese set had 80 cards in the main set, plus 33 cards in the Team Magma deck and 33 in the Team Aqua deck. Minus repeats, there were 132 unique cards in ADV4/EX1. ... Since EX Sandstorm had a number of cards found in ADV4/EX1, and presumably EX Dragon will have some as well, the English release of ADV4/EX1 might be around 80 or 90 cards. Perhaps. Maybe. Don't hold your breaths.
Set Order: 22nd set in Japan, ??th set in the US
Release Date: October 24th, 2003 in Japan, ??? in the US.
This set is the first set to introduce Team Magma and Team Aqua Pokémon and characters into the game. Innnnnteresting.
Although technically the fourth set in the ADV series, this set is officially known as "EX1" in Japan (as opposed to ADV4). More proof that the Japanese want to be Americans when they grow up; the use of EX in the title is nothing short of what Nintendo of America did with the ADV series when they released it in English.
This set also introduces another first to the game, dual types. As in Pokémon are of two types in the game (as opposed to one). This set however deals with Darkness-and-something-else type Pokémon. But it's not like dual types is anything THAT new....
Certain cards from EX Sandstorm can be found in EX1..... meaning that WE got cards before Japan did. WOW!! ... But considering that some of the cards in EX1 were in EX Sandstorm, don't expect to see them reprinted in EX1-in-English.
The symbol for ADV 4 is a sort of 4-sided star burst.