I remember when the trucking industry was switching from the standard 48' trailer to the 53' versions (the old 40'-45' really felt small). Five more feet to worry about...oh my. :E
I wouldn't worry about the extra 5'. You are stepping up from what, a 8, 10 maybe 12' box??? The change from something you can see over, to something you can not, plus the added legnth, will be the biggest shock to your system. Whether or not it is 24' or 29', will not be of much concern. Both of them will pull roughly the same.
You are going to experience a learning curve....might as well get the TT that suits you best.
I would get the one that makes the wife happy. :B
WEIGHT POLICE: Enter comments here on how the 29' will weigh more, have more storage (read cargo weight), etc, etc, etc.... I am sure the OP understands that bigger means heavier, in most cases.
I read the OP's question as being one of size, not weight, as they already stated a desire to stay well below the limits of their TV. Therefore, it is my OPINION that the change from pup to TT will be the biggest change, and whether it is 24' or 29' won't make much of a difference.
EDIT: Dutchman snuck in there, so I want to add to what they said.
I met a man with a 40+ foot 5er, and asked how many it slept. He said: "two". Then went on to explain that it had one bed, that belonged to him and the wife. The couch, was a couch, for them, but if the grandkids wanted to come along, they could make it a bed. Same with the kitchen table.
In other words...do what the Dutch has expressed. Get a trailer for the two of you. Anyone else can make due with the space you allocate to them.
What does a couple do with "Bunks" when no one else is along...which is probably MOST of the time????