The EMP attack would be far less deadly.

To start off with a baseline,12 nukes going off in our 12 most populated cities means 10's of millions dead and millions more dying from radiation over the next year. Overwhelming any infrastructure left in cities surrounding and not affected. This would also mean an exchange of strategic nuclear weapons that only ends in the entire North American and European and Asian continents left dead and likely the entire rest of the world dying in the nuclear winter to follow. This is mutually assured destruction and everyone owning these weapons has agreed they don't want that.

For the EMP attack to be close to that deadly you have to make a lot of assumptions that just don't add up.

First the delivery of a weapon of the size needed to strike the majority of the US at the altitude needed to allow delivery of the pulse to do enough damage would appear like a first strike weapon and result in the same mutually assured destruction because our response would be fire our strategic nuclear weapons in return and everyone else would follow suit.

So large weapons that would impact the majority of the US aren't worth worrying about because we all die anyway.

Second, a smaller weapon delivered high enough do broadcast damage to the majority of the US isn't strong enough to do much beyond bring down satellites in it's direct line of sight and maybe electric grids in a specific area below it. While this is a threat and a hypersonic weapon carrying a nuclear payload would fall into this category.
Worst case scenario is something like this going off in orbit over Maine impacting the north east seaboard and shutting off power. Likely vehicles, small electronics, personal radios, even cell phones if insulated inside a building and any electronics that are powered down would survive. The cell communications would come back as soon as portable cell towers were powered up. Aid would begin flowing into the area from surrounding states immediately and transport of patients from hospitals would begin rapidly. This likely causes local chaos and looting and some deaths will occur as a result until National Guard and Police units can enforce curfews and keep things under control. Think post Katrina New Orleans but without the flooding.

Third, any kind of man portable or private plane delivered device would be too low in altitude to do much. The electron wave only goes to the line of site and any device that small won't have enough payload to do much beyond a very limited area.

Finally, assuming all the above is not true and the scenario described in the book happens you have to also assume that the entire rest of the world would refuse to come to our aid. While it would be very bad for a period of time eventually aid would come, infrastructure would be rebuilt, and life would go on.

So no an EMP strike would not be anywhere near as bad as a nuclear strike.

I'd rather live right next to a major military base and be in the first group to get their ticket punched.