It's interesting that you mention cargo space.
We fulltime (in the UK) and have a 34RLSA on order - currently in a Keystone Challenger 34TLB.
The large locker in the 34RLSA will be slightly smaller than we currently have - but if you are going fulltime you need to seriously 'reduce' the amount of 'stuff' you carry around with you! We spent months selling just about everything we own on ebay last year, and even the missus gave up lots of shoes and handbags!!!
The most important thing is to get the layout you want for fulltime living - and make sacrifices elsewhere ie. the 'stuff' of life! Your living space is where you will be - not the locker!!! Just a few tools, seasonal clothes, outdoor furniture and a BBQ! (oh - and in my case plenty of beer!!!)