This is my first time I play bg2 so What should I choose?
Shadow Theifs or Bodhi?

<font color="lightblue">It doesn`t matter in the end.
Bodhi`s quests are slightly harder, but better in terms of the items you get.
Think back to Irenicus` Dungeon, and the fight in the Promenade; then think about who Bodhi is- you might figure out something about her that she isn`t letting on, as such... this may help you decide. </font>

ok, thanks

<font color="gold">Though it doesnt matter, siding with Bodhi is the evil path, siding with the Shadow Thieves is the good path.
But again, doesnt matter which you choose. ;) </font>

<font color="lightblue">Ah, but that can change as easily as your class... I am going to have my Undead Hunter side with Bodhi... she is obviously a vampire, and so by siding with her; he will be far closer to the scum which he has devoted his life to, not avoiding, but anyalating. Thus, as far as he knows (even though *I* know differently ;) ), he is closer to wiping out the undead scum that rival the Shadow Thieves. </font>

I like to look at it from my char's point of view. Would I really want to ally with a small guild and make the Shadow Thieves, who span all of Amn and have contacts up the wazoo, my enemy?
Spoiler that might help you decide
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You end up fighting Bhodi anyway. If you side with the Shadow Thieves they'll help you, but you can't avoid conflict with her and her guild near the end of the game.

ok, I choosed bodhis, I will go and kill the shadow thief boss know

Little spoiler tidbit
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If you fight for the Shadow Thieves, you can go back and enlist their help in Chapter 6.

Yes but there are better helpers in Chapter 6 - and they do not depend on whether you are siding with Bodhi or Aran.