Your question seems directed towards ordering a new Alaskan and as a part of that, do you need a flatbed for any other reason than to order one with side doors.
OK, my response is in regard to my older 1960s NCO and my current 1976 CO.
1) the NCO requires sleeping east/west so climbing over your partner at night is a problem.
2) my CO requires sleeping east/west as well so if BOTH campers are up in the over-the-cab sleeping area you still have to climb over.
3) the NCO sleeping area is only 48" wide. I suggest you mark that on the floor with tape and try to accommodate two ADULTS in that space!
4) with regard to storage space; my '60s NCO had upper storage cabinetry and my CO also has the same cabinets. Both have the drawer under the table location.
5) if two adults go with the CO then one can sleep up and one can sleep down. There is still the issue of the upper berth sleeper having to crawl over the lower berth bunk to visit the toilet.
6) however, if you go with a CO and have only two adults, the upper berth sleeper has enough room for some of their personal items like clothes or the things your lady might need on the trip. The lower berth will still have to be transformed back to the table set up for meals during the day but the CO has a place to store the bedding....in the upper berth whereas the NCO does not.
7) as far as wind resistance with the CO vs the NCO goes...there is maybe 16" or so of the camper ABOVE the roof of the truck that you don't have with the NCO....if the cost of gas/diesel means that because you drive 10,000 per season with the Alaskan that the fuel savings vs the COMFORT of the CO is important to you then go for it....lessee...10,000 miles in the NCO at 14MPG is 777 gallons @ $3.50 is $2,850 a year. The CO might get only 10MPG which is 1,000 gallons which at $3.50 is $3,500 a year. A difference of $650 per year. These are ROUGH estimates, However, you spent $40-60,000 for your truck and maybe $15-20,000 for the camper. That is maybe $80,000? Is $650 worth not having the COMFORT of a CO Alaskan? Well, I've had BOTH and there is NO comparison.
If you are going to order a new rig and are close enough to the factory to visit once or twice, you can see the layouts as they build them and see how much/how little "room" you will have with any of the layouts including the side door (flatbed truck) style. With the flatbed/side door layout you pretty much have dedicated that truck to keeping the Alaskan on it all year long. If you are planning on year-round use then mounting/dismounting it is not practical. If you need that truck for non-camping duties and especially if you need a standard 8' bed to mount a camper SHELL on the rest of the year then the flatbed/side door style may not be right for you.
A big part of this is also how many people will be camping/sleeping/eating in the Alaskan...if you have more than two adults then a NCO is like a small boat; not very big, no storage space and no room for more than two at the same time in there and sleeping arrangements are difficult at best.
We had the NCO years ago when we were younger/hardier and could deal with a 48" wide sleeping area for TWO adults. As you get older you will not find that comfortable at all once you check out a CO set up!
Remember also that an 8' 3/4 or one-ton truck can easily handle an 8' CO Alaskan.
If you went with a 10' CO you would definitely need a one-ton.
