Rush BT or IE?
As an ADC I would usually rush BT, but tell me what you get and why?
As an ADC I would usually rush BT, but tell me what you get and why?

BT turned into a mid-late game item because it doesn't give you AD anymore.
Okay, I normally get BT because sustain. It helps when you need to hold your own laning.
Others rush IE for extra crits, which is fine if you are covered all the time and can secure the kill on your enemies.
So... BT if tied/behind IE if ahead + aggressive.
IE. One crit with IE is worth 2.5 AA's which is huge
The standard is to run double Dorans, infinity's edge and bezerker's grieves, in that order (tier 1 boots can be purchased at any moments). The reason for that is the lifesteal on your runes + lifesteal on your 2x Dorans should be sufficient during the laning phase.
Furthermore, Phantom Dancer or Statikk Shiv can be purchased right after which continues the "critical strike chance" patch. This ultimately gives you more damage. Bloodthirster is better as an 4th+ item.
IE always, out damages BT by far if you get that crit. If I'm behind I get brutalizer to ghostblade because the components are cheap