I believe they are both one and the same, I looked this up on another site and this is what I Found:
Lewy Body Disease is comprised of a spectrum of diseases involving an array of dementia and motor symptoms. It is commonly referred to as:
Lewy Body Disease
Lewy Body dementia
dementia with Lewy Bodies
diffuse Lewy Body Disease
I understand your frustration with wanting to know what to expect but that can't really be predicted, I always believed that the course of the disease was from 5-7 yrs but I believe my Husband had it at least 9 yrs, I really don't think age is a factor, My Husband was only 66 yrs old when he died and that meant he started when he was 57 yrs old.
I hope this helped some, Come back again and ask what you need to and someone will try to give you some answers!