We've only had two hiking tents to date so i cant give you many comparisons, just let you know that we are happy with our choices. We got two tarptents - the Hogback and a Double Rainbow. My husband is 185cm (6ft2) and we have the length in both to have our packs inside with us. We chose the Hogback for use with our 2 teens and the internal space, especially height, is fabulous. Our 13yo son is growing rapidly so we need space! I liked the freestanding aspect of the DR and it's rain/shade porches, though It's not as spacious inside as the scarp 2 would be (the Hogback has the same profile as the Scarps and is effectively a Scarp 4). If you are considering Tarptents, then also think about some of the new ones just out. Take up Franco's offer for a look!
We've used both in Victoria in a range of weather and locations, most recently the Beeripmo Trail and Lerdederg Gorge . It's rained on every overnight walk we've been on in the last couple of months and so far they've done a good job. The ventilation seems to be working as we haven't had any condensation drips. The full enclosures with lots of mesh for bug protection has worked well - hubby is a mozzie magnet. If we have a warm night with no forecast rain I'd probably leave the fly open on either tent so there's lots of ventilation through the mesh.
Kids grow quickly so I think you are better off getting a 2-person tent. Young kids also take up more space relative to their size than we expect because they wriggle about so much. Since you'll be carrying for two, lightweight will be an important consideration.