Depends on what you mean by "good," and what it is you're actually trying to treat. It's essentially all symptom management-based for most of the populations and conditions with which we work. So if a person with dementia is having behaviorally-based difficulties, you can work on implementing various behavioral strategies and plans. If someone is having cognitive difficulties, you can either work with them directly on developing compensatory strategies or refer them to someone who will. If they're having difficulty adjusting to their illness or injury, you can assist them with that (or, again, refer as needed). If they're having trouble with sleep, injury-related pain, or medication adherence, again, you can use various targeted therapies to address those issues.
This would be the advantage that a neuropsychologist would have over a neurologist in this case--access to the various therapies that most clinical psychologists will have in their toolbox. Depending on the neurologist and their interests and training, neuropsychologists may also have more exposure to differential diagnosis amongst some of the various dementias. Conversely, a neuropsychologist isn't going to prescribe something like donepezil or memantine, although I don't know that this is necessarily a bad thing given the limited utility of the medications. Also, a neurologist is going to be better at quickly picking up various other neurological conditions (e.g., neuromuscular disorders like myasthenia gravis, neuropathies like CMT, etc.) and will have access to the types of tests you'd need in such situations (e.g., EMGs, muscle biopsies) as well as medically-based treatments (e.g., anticonvulsants, migraine meds, TENS--although that might go through physiatry). They're also of course going to be able to draw on their medical training and use that to inform diagnostic and treatment decision-making.
