I think the main problem here is differentiating between Arimidex and an Aromatase Inhibitor.
Neither of which are essential in most cases while on cycle with Nolva and Clomid clearing up PCT.
Personally i've always kept Arimidex on hand during cycle just in case, but have never had to use, whereas some people are just pre-disposed to estrogenic sides and can benefit from either or.
Both will work fine but don't run them alongside your cycle till u notice sides where treatment is required as there is still some dispute as to their inhibiting affect on cycle.