I have a 28' 1968
Ambassador and I have towed my friends 28' 2004 safari. I tow with a new 2008 Sequoia with the big motor and tow package. To be honest I really didn't notice the 2000 lb difference that much, it was a little more effort up the hills but not much. I could still pull either on up the mountains faster than I want to. We live in Colorado.
It's going to come down to you Tow Veichle and your hitch set up. like I said, The difference was not that great but I could tell there was more weight with the newer one.
Now the wide body I would have to get extended mirrors for as it was hard to see around.
With my trailer I can see around. Also I found it easier to back up my trailer as I could see more.
As for sleeping 5, If your kids are young they can share a bed. Our friends front coach folded into a bed and so did the dinette. They have a queen in the back.
The nice thing about the older trailers is: you don't feel as bad tearing out the inside. I am in the process or redoing ours. I took out the 2 twin beds in the mid section and put bunks in for the kids on one side and a small dinette on the other that will go down into a twin bed. The coach in the front folds down into a queen. So we can get five if needed.
I will come down to time and money. It's tough to find an old trailer in good shape and if you do the decor is old and dated. Though some like it.....
So then it comes down to a remodel. If you buy vintage make sure the frame, axels, and floor are in good shape as this will save you time.
The new ones will cost you and be tight for sleeping 5 but then you don't have to do anything to them...