Hi Richard,
I only have 2 kids and went through the same process. We're moving from a Jayco Eagle back to a soon to be picked up Trackabout Dakar Extenda.
Wanted a Hard Floor, but based on the storage requirements we needed, and price, we went with a soft floor. I went to every camping show in QLD over a couple of year period and still do not believe there is a perfect solution to everyones camping needs.
This is what I found when comparing the newer soft floors to a hard floor. People will disagree.
Set Up Time - Overnight without an awning = Hard Floor quicker. If setting up a full awning, the hard floors are no quicker as they usually have more awning poles than the smaller soft floor setups such as the Complete Campsites and Trackabouts. If setting up kids rooms/extra tents on a hard floor, they are no quicker than a soft. Pack up Time goes in comparison with the above, but the soft floor is sitting on the ground and depending on site/weather conditions can need a clean up, so can take longer. When setting up/packing up, its the all the crap you take with you that makes the process longer and not so much the tent.
Ability to sleep kids - Soft Floor wins without a doubt, unless you've setup in a low area and it gets flooded. In this case, youll wish you had a hardfloor.
Storage - Soft Floor has more ability to store extras. Eg under the tonneau on the Trackabout we will be putting 4 x chairs, table, 2x kids swags, solar panel, canvas bag etc. Some hard floors struggle to close even with the awning attached. Some dont, depends which one you get. If getting around with 6 kids like yourself, the soft floor will definately be a better option storage wise.
Kitchens - Hardfloors more than often had the advantage here, but the newer softfloors have more than made up ground in this area. The top of the range softfloor kitchens are now equivalent.
Weight - Once loaded bugger all difference between a top of the range soft floor and a hard floor. Hard Floor slightly heavier.
It's my opinion only, but if you are comparing a standard soft floor to a standard hard floor, with a family of six a soft floor would suit better. But thats my opinion only, and what works for me may not work for you. This does not take into consideration campers such as Camprite. They are different again and have their pros and cons. I looked at these too (secondhand) and chose to go in another direction.
In saying all this, I would have liked a hard floor due to being up off the ground that little bit. But it didnt suit my current requirements with the kids. It might later on. If I could have got an Aussie Swag that comfortably slept 4 for the price of my Trackabout, I would have bought it. (As well as a roofrack to go on my Prado) A hard floor for a soft floor price, thats not asking too much is it?
Campers - If you end up leaning towards a soft floor, have a good look at Trackabout. I checked out the Complete Campsites, Mountain Trail as well as the Trackabout and they were a lot better value for money. Check out the "My Camper Trailer" section of this forum and have a look at the Dakar Extenda which is currently being built for myself. The Trackabout website does not show this camper as yet but will be getting updated soon apparently.
Anyway, all the best