Your system either has Ich or it doesn't.
The type of fish you get doesn't have any bearing on that so long as you QT and prophylactically treat for Ich before introducing new arrivals to your display tank. (this includes corals and live rock/sand, and anything else that could harbor an unhatched Ich cyst.)
If your system already has an Ich infestation then no matter what kind of tang or fish you introduce, you are taking the chance of the new fish succumbing to the infestation and dying and/or setting off a chain reaction in the other inhabitants.
If your system doesn't have Ich then it doesn't matter what type of fish you get, just so long as you follow proper husbandry and treat it before you add it.