I'll add to myredraer and suggest that when you find some floor plans you like, don't be afraid to test all the areas that you will use. Go into the bathroom, shut the door and sit on the toilet (lid closed:)), stand in the shower to see if there's enough room, step out see if you have room to dry off.
Sit on the dining seats. Is it a booth? Most are really uncomfortable after 10-20 mins. Just sit in them for awhile to see how they feel. Not all are the same.
Basically try out the trailer as if you were going to be in it to use it.
I've read so many posts about owners that complain about things that could've been eliminated had they did a better walk around before they bought it.
Also check to see what's accessible when the slides in. Not everyone worries about it, but many like access to the fridge or toilet while on the road. It's much nicer to be able to use your own toilet and then grab a bite to eat from the fridge or pantry.