The nicest part about having an integrated unit is the ability to navigate most road infrastructure and parking lots. There are a lot of places where it's either no fun or literally impossible to navigate with a trailer. For instance parking in any city-like environment. That includes dinky "cities" of 20k people.
As someone that camps otherwise stock van with a sofa bed every type of camping system has it's advantages, disadvantages, and costs. Show me any type of camping setup and I can tell you why it's non starter for a lot of people. And perfect for others. My take about electric RV's is essentially RV's are all built on a van, truck, or bus chassis. When those become available with enough range you'll see RV's built on them as a standard option.
I also am "full time" nomadic during the summer months, so if I want to stop in someplace specific I do it on a travel day in between campsites.
My ideal setup:
* Class B - day traveling and occasional overnighting. For example, being able to pull over just about anywhere for a nap while driving.
* Small Trailer - Camping equipment, shower, beds, etc.