I know some of the input I will be looking for here has been discussed in part in lots of other threads, but I wanted to start one more pertinent to my own build.
When the U-shaped dinette first came out, I was not liking the idea all that much, as I could not fathom losing table size. A large table was a bit part of how we used our 19, as it was a marshalling area more than an eating area, as to date we mostly eat outdoors. Camera gear, clothing, dishes, food, etc all was temporarily set on the table. This was handy in the 19, as the table is right by the door.
Now moving on to the 5.0TA (with the same dinette as the 21), I started to reconsider. I do like the look, and there is a good chance we will spend more time in the trailer in the future, with quite a few extended trips planned. I quite like the idea of an area where one could lounge a bit. Some loss of table size is not as big of a deal, as we would not use it for temporary storage of items going in and out of the trailer, as it is far removed from the doorway. Plus, the dinette is wider than in our 19, so the loss of size would not be that big.
I had never actually sat in a U-shaped dinette until a few weeks ago, in Chris R's when we visited him and Ida in Victoria.
As it turns out, the added rear bench is not really useful as a seat, as it is to narrow to sit on. As well, I was very turned off by the limited floor space. We do entertain other couples, often playing cards at the table, and with the pedestal there, there really would be little room for four sets of feet. Very cramped.
Why would the U-shape be any more conducive to lounging? Is it a wider place to put feet up? If this was the case, one could easily just add a board across, with an extra cushion on top.
I do realize there is storage space gained, because the batteries and converter panel both get housed under the rear bench. That is a plus. What I wonder, is could this rear bench be made even narrower, and yet still house these components? This seems like a winning situation if doable, as it would only make the unusable/unneeded seat narrower, and give more floor space. Maybe even if it house the converter and a few other electronic/electrical items, and the batteries are moved, it could definitely be made a lot narrower.
As a bit of a side note, I am considering AGM batteries. Am I right in assuming that they don't need a battery box and venting? This alone would allow a couple more inches for the back seat to narrow.
Even if I went with a U-shaped dinette, I would likely forgo the rear backrest, and instead just have two large throw pillows, that could either be used in a back corner, or against the galley or fridge cabinet for when we want to stretch out and put our feet up. Again I wonder at the need for the back bench to facilitate this.
To be honest, with the cabinet work I plan to do, I will extract hordes of usable cabinet/drawer storage, so any not gained with the U-shape, would be more than made up for.
Whichever way I go, I plan to do the single Dicor pedestal with the 4-way sliding top. I also plan to have the table to be resized, most likely by folded the outsides on top of the middle to create a table half the size. Plans can, and do change though.
This is a table top like I am describing.
This is just a wee insight to about 2% of all the considerations and planning I have done for my upcoming 5.0TA, but most I got figured out already. On this topic, I could use some thoughts and input.