Having just retired my old Midwest cage for a Martins I thought I'd give
two cents.
 
Midwest - pro's
- Goes up and Knocks down easy
- Very sturdy
- Bottom door opens so it folds down like a ramp
- Crock lock water bowls aren't too high
 
Cons
- The cage sits in the tray making it impossible to keep clean
- Heavy - as in lifting cage out of tray
- Need to make own floors for space
- 2 doors - if you put in 3 floors - it always seems hard to reach a
  corner to clean
 
Martin's - pro's
- Lighter to move around
- comes with floors
- Has 3 doors making space more reacheable to human cleaner
- the bottom floor tray - easy to slide out to clean
 
Con's
- Once up does not disassemble again (at least not easily) so awkward to
  move
- The tray set up means the crock-lock bowl sits up to high for my liking
- Assembly - all those little rings - this is not something anyone
  arthritic wants to do
- The ramps - the way they attach to the sides - they sort of bend a bit
  to the unsupported side and my ferrets don't particularly like them
 
I think if your an apt dweller who moves from apt to apt the Midwest might
be more suitable.  Other than that the Martin's is good.  I do wish I
could get a crock-lock bowl lower somehow - Older ferrets don't need any
obstacles to drinking lots of water.
 
"Animals are not brethren, they are not underlings; they are other
nations, caught with ourselves in the net of life and time,"
   Henry Beston
[Posted in FML issue 3600]