Neurology is better known and better respected than PM&R, hands down. But otherwise I think PM&R wins in every other category:
1) Income
2) Hours
3) Available procedures
4) Stress
Neurology can lead to the same end point as PM&R. I've heard of Neurology guys staffing rehab. wards, which is usually done by Physiatrists. Neurologists also do procedures like EMGs (though they need extra training beyond residency for this) and even interventional pain.
If that's the case though, why not just do PM&R to begin with?