Interesting note on Gantz' choice of words
For the third option, Gantz offers the choice to "revive" someone from the memory. What's interesting is the word he uses for revival, 再生 (Saisei) also means "Playback/Play". It's what you'd see on a VCR or tape player to play or unpause a movie/tape.
Judging from Sakurai's reaction to being revived, it looks like everyone's memory gets "Paused", theeir data is loaded into Gantz, and when you revive them, it's basically like pushing play on their life again, starting them from exactly where they left off.
This means that both Tae and Katou will definitely keep their memories up until the moment they died. Tae may not even know Izumi killed her, and Kurono will probably tell her he kicked everyone's ass and saved her (so as not to upset her, not seem cool).
Of course, then he'll probably tell her to change schools and never go near Izumi again :P
lol, just wanted to say that they are copied then paused, because when they are transfered back into the room, with injuries they can only remember to the point of recieving the injury....urgh can you get what im trying to say?