Each transformer has advantages and disadvantages to using them. It’s going to depend on the application that you need them for. That being said, here are a few advantages that each one offers.
Toroidal – Higher efficiency, inherent EMI shielding, minimal signal distortion, compact construction, low heat, small off-load losses.
E-I Core – Lower cost, lower inrush current, multiphase system use
There are exceptions to each one, but generally speaking these are the advantages of both.
