The BN&NP programs, broadly speaking, come in two flavors: dementia heavy programs and broader/general BN&NP. My opinion, for what it's worth (not much)...
UCSF is unparalleled in what it does. They have a focus on frontotemporal lobar degeneration (FTLD) generally speaking, but the research coming out of there is absolutely top notch. Bruce Miller is one of the nicest, smartest, and caring people you'll meet. They were recently awarded a $177 million dollar grant to develop a global brain health initiative. They're the primary administrative site of the ARTFL study, the main goal of which is to discover and develop important biomarkers for future trials in frontotemporal lobar degeneration. There's a fairly strong focus on progressive supranuclear palsy syndrome since the clinical phenotype is strongly predictive of the pathology.
Mayo/WashU are fantastic programs, WashU is very Alzheimer's heavy. Mayo has Cliff Jack (radiologist who was the main PI, I think, for ADNI), Brad Boeve, Ronald Petersen.
Cleveland Clinic Las Vegas is poised to be a huge name as well. Jeff Cummings (a giant in the field) is there and has moved strongly towards clinical trials.
Brigham and Womens and MGH both are great programs as well and have very well-funded and well-connected people doing very good dementia research.
Columbia has a huge public health/epidemiology slant.
This isn't an exhaustive list, and failing to mention a program doesn't mean anything.
As a resident, my opinion is that you should go somewhere that will give you exposure. If you'd be happy at any of the above, you obviously can't go wrong. They are all fantastic programs. If you'd hate living there and have reason to be elsewhere, try to go somewhere that at least has a behavioral neurologist. It's a very small field and having someone who is already part of the club will be helpful when it comes time to get into a fellowship.
There are other excellent programs within the UCNS BN&NP listing that focus less on dementia and more on a broader view of what the specialty is. Some of the above programs will basically give you both (e.g. BWH and MGH both have very active dementia as well as neuropsychiatry programs) whereas others will really and truly be programs designed to turn you into a dementia specialist (e.g. UCSF, you're going to be doing all dementia, all the time). There is nothing wrong with either approach, it's just important to know what the program you're looking into will train you for.
Hope that helps.
RS