Played with coilgun some more, and EM Rifle still is hands down better IMHO.
Killing things through walls tends to be a yes/no proposition, and yes, you kneel just inside the harvester while 1-2 guys lens out the bands, yes you can clear out the UFO with no risk, less ammo cost, and more sniper skill practice.
As for long range shots, coilgun is not accurate enough for eight shots (2 plus 3x2 for reloads) to last a long mission and far from needed in a short one. Now if not for the EM rifle, it would be that or plasma weaponry (with which I am unimpressed) for no alien materials used assault weaponry. Then I would consider it. I would also consider it if I started running into stuff that it took like 10 Bolter hits to kill.
The flavor text implies that the coilgun does not provoke reaction fire. Can anyone confirm or refute this?
Laser tag (you didn't expect that light gun to actually kill a heavily armored target, did you?) and NERF rapid fire skill practice weapons (again, machine pistols are for target practice), the more I use the EM rifle, the more I love it. That said, it is straight up FUN to emptying a machine pistol or double tapping someone with a handgun. Point blank MG full auto and air burst GL burst retain their 15% gratuity for enjoyable, well, gratuitousness.