i dont know much about the game. when i reserved RE4 from gamestop the day of release (which i didnt get till the day after thanks to UPS!), my buddy whos the manager there told me that umbrella chronicals was going to be compatable with the new wiimote gun comming out.
i asked him if RE4 was capatable with any sort of gun (since ive seen TONS of 3rd party wiiguns on www.dealextreme.com) and he said he wouldnt know but knows for sure about umbrella chronicals. he said a big difference is the fact that in RE4 you see your character. in umbrella its just the screen and you dont see your guy. i like that option much better.
all in all, id consider buying this game since i love FPS's. i am midway through RE4 and by the time umbrella comes out, ill be long since done with RE4