When i was looking around for mine i found the best way was to have a feel.
I tryed ones like the ARB and as soon as you grab it, you think it is a bit thin. Also the matress is a big factor.
I had a howling moon in the end and it was great although i find the roof tents a bit of a hassle to pack up which is why i've gone down the Oztent route. Much better if you are staying somewhere for more than one night as you can leave it up.
I had a crawl in one of those Magiolina hard shell type affairs a while back and it seems to be the best combination for ease of putting up and down and comfort.
Oztent is better if you have to get up in the night after beer as you dont hurt your feet, although Plumbo in the other place has a great solution for this problem Is he on here yet, welll worth hearing it.
I have given it to the powder coaters and they have called me to say when they were cleaning it up a few chunks have come off the cast part of the hinge so i need to go and look, don't think its serious but was thinking of making some custom hinges anyway as i want to mount the hi-lift close to the pivot point.
I looked at the oztent but they extremely expensive. I own a VW Syncro 4x4 Camper (looking at a Cruiser very soon) and I have a Khyam Motordome awning which goes up in about 2 minutes and spacious at 3 x 3 metres. I reckon it could be easily adapted to connect to the back of a landcruiser. I intend on giving it a go when I get my Landcruiser. They cost around £200. I am on my second in about 8 years. First one still going strong just needed a taller model for my taller Syncro.
The one time we used our Maggiolina for family camping we used an Outdoor Revolution Movelite XL drive away motorhome awning, connects very nicely to the side of the Maggiolina and gave us somewhere to leave our tables, chairs etc when we went wandering and packs down quite small. Would also connect to the back of a cruiser. More recently I've noticed the RV Room M300 which looks much quicker to put up, similar in some ways to the Khyam system, not sure how small that packs down though.