Here are some older pics. There currently are 500+ bulkheads and there are several smaller floor plate towers, an Outlander building 6 bulkheads tall, and similiary upscaled version of the "Storm of Vengeance" campaign pack. It all spreads to two and half feet wide, 9 feet long, and 6-7 bulkheads tall. A main wall runs 6-7 bulkheads high and 9 feet long, with portals through to the outside of the hive or hive dome. Each of the original building floor plates has been replicated into one large building keying on that plate's shape and function. Thus the condominium, arena, and industrial type constructs. I have added long and short gangways, stacked gangway assemblies, and magnetic retaining system for the gangways connecting to the buildings on most floor plates. The 40K buildings almost fit on the rest of the 4'X8' piece of plywood. Sorry, all is stored now on shelves. It is all sitting on an octagonal poker table I made.
And guess what?
You nutter. That is amazing!
Going back to the original post I favour a mix between the two. Areas of crazy density and some areas that are less dense. Ideally I'd like a story to the board, i.e. small industrial sectors with loads of walkways, maybe a road or wasteland in between with lots of scatter but no LoS blocking terrain in it and maybe an area of Hab Block etc. Some gangways the separate zones and some solid risers to LoS blocking. However with the terrain I have (mainly card walkways and plastic bulkheads) this isn't always possible but as my collection grows hopefully it will be (as I'm hoping to buy and build more unique looking pieces).
This is why Mordheim is so cool for terrain as you can create dense rows of houses, some with little alleyways between which making a series of larger roads that are concerned to a town squat etc and you don't have to worry about a H.Bolter killing field!