We looked at a 2003 model this past weekend and I'm hooked on the 400.
The cockpit, galley space, and master stateroom were highlights for me.
Right now I can say I choose the 400 over the 42, not in any order, because:
1. Galley has more usuable counter space.
2. Navigation table location.
3. Port bench in cabin is long enough to sleep on.
4. Master stateroom is huge. Need to see it to understand.
More to come?