I have the 2017 Volt Premier with ACC, can only comment based on what I've read about the ELR. Seems that if you are OK with basically a 2 seater, looking for a more richly appointed interior and a rare, stylish car then maybe the ELR is for you. I believe it has rear seats, but not as usable as the Volt's. Also, I believe the range on the ELR is more like a Gen1, so around high 30s all electric while you get low 50s in the Gen2 Volt. You also get the cache of a Caddy vs. a Chevy if that's a factor.
Others with experience with both will provide more insight I'm sure...
Others with experience with both will provide more insight I'm sure...