For a manned mission to Mars, you can either go slow (using conventional propulsion on a minimum energy transfer orbit) or fast (using some form of more exotic propulsion). And you can either go in a small, cramped low-mass habitat, or something heavy but spacious.
Obviously, fast and spacious would seem to be the way to go. However, fast and cramped would be okay, and possibly slow and spacious would be acceptable. But evidence suggests that slow and cramped is a fast route to psychological failure.
A fake mission to Mars with six trained “astronauts,” in a small “spacecraft” that took 17 month led to four of the six being more or less useless wrecks well before the end. Of course, these were six *men,* no women; that could be problematic (of course, having men fight over women – or women fight over men – would not be much of a help). Having this be 17 months in microgravity would only make the situation worse… probably *far* worse.
Fixes for this would include:
1) Bigelow-style inflatable habs to increase volume, so the astronauts can get the hell away from each other
2) Much larger crew complement so people don;t have to stare at the same faces all the time
3) Send Mars landers, habitats, infrastructure, etc. ahead of the humans via efficient-but-slow, but sling the humans on a sprint trajectory using advanced propulsion such as NERVA, Orion, Medusa, etc.
Seems to me the best answer would be to go with a 4,000 ton Orion vehicle with a crew complement of a few hundred. Get there lickety-split in comfort and style.