I would say yes, camper tents are usually colder than tents. We have come from a touring tent background to a camper trailer. A lot of it comes down to the greater internal space in a camper. For us this is offset by the extra comforts as you say. We sleep with two doonas in winter and are toasty warm.
This is our experience as well.
With the old canvas touring tent, we'd zip it up reasonably tight, and it was really good at keeping the heat in. The camper, with it's bigger internal volume seems to lose the heat as soon as the sun goes down.
That said, I wouldn't have it any other way. We've counteracted this by not trying to keep the tent warm - leaving the window near the bed open to get fresh air through and enjoying being able to look out through the night from the comfort of the blankets.
Of course, my definition of "cold" might be slightly different to that of people living down the bottom end of this country...
Thanks!
Matto