We went down the fixed twin beds route in our Adria Adora Seine. We started with a 2006 two berth to see if we liked it - our conclusion was that we enjoyed the weekends away but wanted proper beds.
The beds take up a bit of the length of the caravan but compared to the two berth, the luxury of not having to make up the bed at the front is worth towing something a bit longer. Like OD, we cheat with a motor mover these days. I am confident reversing trailers but longer vans are a lot of effort in the tight spaces you get at some sites and after a long journey towing, I just want to get pitched and open a cold one.
We bought a second hand VW Touareg for not a lot. Like all cars of that size, it is not an economical option (the VED is nearly £50 a month) but it tows the caravan and horsebox like a dream and we have no issues with kerbweight. The Caravan and Motorhome Club also has a vehicle matching service which seems quite nifty but it is surprising how big a car you need even if you creep up from 85% towards 100%. Basically, you are in Touareg, Discovery, Range Rover, Q7, Mercedes M Class etc range if you want to tow the bigger modern vans.