I have only tried smoking using electric. I wouldn't mind trying charcoal at some point to see if there is a noticeable difference in the taste. The biggest challenges that I have experienced with the electric are:
-Hard to control the temperature. Usually it will hit around 220 - 240. I have not been able to get anything lower on a consistent basis. I read that using a dampener can help reduce the power of the heating unit and better control the temperature so I have been looking into investing in one.
-I initially had problems where the wood would burn too quickly. I was able to remedy this by using soaked chunks as opposed to chips and making sure that the lava rocks were more thinly spread around the wood chunks. My last smoke went for three hours without needing to add more wood.
-Like the charcoal model, the electric model ventilates the smoke from the opening in the lid. I plan to seal the lid and drill some holes in the top of the lid to allow the smoke to better pass through the meats. Especially the meats on the top rack!
Despite these challenges, I am able to get pretty tasty results. Plus, the thing is pretty easy to clean and maintain.