I don't know enough physics to comment on the effect of different media on EM emissions but from what I understand any potential effects would not be significant enough to negate an order of magnitude difference due to the the nature of broadcasting or even beam-forming a stream of data v.s. sending it down a physical channel that is in comparison a point to point use of resources to manipulate bits (ALU ops, SRAM r/w, Flash r/w).
Might be able to find the paper I'm referencing. Will post tomorrow.