I used a fair amount of IMC and GRC in hazardous locations including 4-20 mA control circuits and VFDs. Never noticed a diffrence in EMI or RFI problems in one over the other.
Although lighter in weight the IMC was indeed harder to bend, and keeping the shoe tight against the pipe for an accurate radius was difficult even at the 3/4" size. I would avoid using it for hand bending.
