Its preference, based on how right you want to do shit. Cold side next to throttle body is obviously the way to go because air will never have to return flow toward the turbo (post closing throttle body) risking surge. The only way to do this without stalling issues is to run a map. Hot side is nice because its easy to recirc so your car runs smooth and 1/2 of the hotpipes out there are sold with a flange on the bitch already.