If I have a big enough group, I like the J2 Fat Trader. It has some legs (J2). It has a good payload (150dtons). It has good accomodations (13 rooms). It has decent enough floorplans. And, best of all, it has its own subcraft (the launch).
Going smaller, the J2 Beowolf is good. Like others mention above, I just prefer the Beowolf floorplans and its looks much better than the Marava. I would even keep the 20 lows.
If price is no object, I like the good ole Type T. It has long legs (J3), some cargo (50 dtons; 80 if you toss out the ship's boat), can be privately owned, and is just a flat out cool looking ship. Floorplans are a bit dicey, but workable. Having J3 is just way too cool.
I tend to avoid ships much larger, though, because at that point the individual characters start becoming "drowned out" by the fairly large crew. Even the toy fun ball has a pretty big crew.