It's two hot to do much else today sooo I figured I'd throw my 2 cents in.
I have 2 brisbanes, and another like a brisbane but it's a different brand and only has one door instead of two. I've had a Dcn as well. I have 4 in one, and trios in the other two.
For the pros and cons maybe different. My living space is not of normal peoples living space standards. I live in a 5th wheel so I have ceiling height issues for me Brisbane's work the best in my space.
The cons- the latches are a pain in the A$$ They are secure, IF you make sure they are latched properly. I have to triple check mine or we have escapes ( it's not really an escape when the door isn't latched
) but it does happen often enough that it's an issue. The latch will look latched when it's not.
You can combine two brisbanes together and make one big cage with some modifying. I've done it and loved it! But I'm not sure if you can stack them to make a double tall one or not, i think someone did and had to put the top cage upside or something.
really the latches are my biggest issue with the cage. It's a heavy wire quiet cage that holds up long term.
Some think the door size is to small and think larger doors are better ( thats a personal preference thing) , some wheels won't fit through the door but it's easy enough to take the top panel off and put it in that way. For newer owners smaller doors are a blessing ( gliders don't get out as easily as the dcn huge doors) If your not that bonded to your gliders or have some that are always right at the door when you go near the cage the big doors can be a pain, but for cleaning and swapping out toys they are awesome.
Both large and smaller doors have benefits and negatives. I will say I do prefer the Dcn latches better there is no way you can accidentally not latch it.
To answer your question about the Dcn, there is a divider panel that is removed and modified to use as the bottom grate to open up the entire cage. Many folks do that.
Congo, Madagascar, Brisbane and Dcns are all good quality cages. You just need to think about the space you are putting it in, if you are going to increase your colony size some day and which type of door you prefer. Brisbanes congos and madagascar are screw together cages the Dcn you just bang it with a soft mallet if I remember right. There are some holes in the Dcn cage on the corner part of the frame, you can get some plugs for them to cover the hole if I remember where the link for them are I'll post it