Hello Proto.
The VW in my avatar is our T4 high top van, which we have had for 8 years now and have clicked up 300+ nights in.
It s the only campervan I have ever owned, so I can't offer direct comparisons, but I had an interesting chat a while back with a guy who owned a pop top T4, and who said that it was draughty. He was asking to look around our high top van, and said that it confirmed his view that a high top was the way to go.
But, at risk of stating the obvious, a high top prevents you from getting into many car parks, particularly in tourist areas, as they have Barriers to prevent the car parks turning into campervan parks.....
Our van has barn doors on the back. Not so handy in wet weather as an up and over door, which shelters you if you need to access the rear storage, but you don't need to leave as much space behind you and still be able to get the back open. I wouldn't regard either sort of back doors as a "deal breaker".
Ours is a long wheelbase van. It gives a much more comfy driving position for me (6 foot 2) as the short wheelbase fans have cupboard units just about touching the back of the drivers seat. It also enables a longer bed and bigger cupboards than the short wheelbase ones. It does mean that the turning circle of the van is bigger and more care needs to be taken when, for example, pulling out of junctions and turning left, if you are to avoid running over the kerb. But you very quickly adapt to it.
PM me if you have any questions......