HI Jude :lol:
I have always had a custome setup, tight from the start and I have found that if for any reason( like me being too eager) you get the wrong thing i.e the light is too short or filter too powerful then you have an easier time changing it than on an intergrated( where you would have to change the whole setup)
With having a custome Ihave external filters that hang on the side and it means I can change the end it sits on to give the fish a bit of change.
As for the hoods, holes and cord, you can trail most of them down the back of the tank, and I just have a pre made light fitting that i purchased and it just sits ontop of the tank, so no hassle with custom hoods.
hope this helps some.
IMHO It also gives you a wider scope for the sizes that you can choose or have made, as you stated above.
B