There's a good difference in size with the two of them. The kampa is probably a little narrow width wise for 4 would be an ok weekend tent but tight for a week. You really need to go n+1 so I'd be looking at a 5man minimum.
They are both good brands I'd look at Outwell too. That Vango is quite spacious 3,0000 HH is still ok. We have a pretty similar sized Vango Illusion 500 TC airbeam and it's great especially on longer breaks. The double doors at the front are handy as you have a wet room area at front to take your shoes and coats off keeping the inner dry. The living space is great on wet days for the kids. It is massive though even it's packsize and it weighs 50kg! It is too big for the odd campsite aswell.
What's you and wife's experience camping? Putting up a big fibreglass pole tent like that solo in wind and rain with smallies crying in the car can be challenging to your marriage vows!
We started out with a 5 man Outwell Nevada fibreglass poled tent it's a nice bit smaller than our Vango I can put it up solo but it's tricky if it's windy. The airbeam is much handier put up despite being a much bigger tent. We have had a few poles break too it got flattened in fairness in what was pretty stormy weather in Doolin when my brother borrowed it and camped with us. A lot of other people had packed up and left. Our Vango Airbeam barely budged! It had stood up to plenty of bad weather before that and it's a nice size weekend tent and takes up a lot less space in the boot. When funds permit I will get a smaller polycotton airbeam to replace it.
There's a bit of expense starting and a good few things to get with, sleeping bag's, mat's, camping furniture and cooking equipment. It's well worth it though once you have it it means plenty of cheap weekends away.
Bit dearer but it's not a bad price for a large airbeam.
Just to give you an idea of size. The fully loaded family trips take a lot as wife likes her comforts and electric hook up. I'm as happy going of in my little 3 man with just one of my kids for a night or two!