Hi Nate,
Just as a bit of background, I have a little experience with a few tents having spent a good bit of time in an ARB, a Howling Moon, and I own a Columbus.
For a while now, I've put-off the thought of mounting a RTT to my 2008 4-Runner for a couple reasons. The biggest being that I wanted to still be able to park in my garage. I've decided I can live with my rig in the driveway during the "camping season" and remove the RTT for winter, allowing the truck to be in the garage during snowstorms (I live in Denver).
Something to consider is whether it is easier to take a tent on and off a rack, or leave your tent mounted to your rack and take the rack on and off. I know people who do both.
Camp alone 50% of the time and the other 50% with my two kids (8/10).
Personally I think that rules out the hard sided tents. I really like my Columbus for camping alone. It goes up and down so much faster than any other tent I have used -- ground or RTT, and it is really easy to leave all the bedding in it. My Columbus is a small and is a nice size for one and pretty tight for two. No possible way to add another person (or dog). Going to a medium gives a little more room for two, but it takes up width on the truck. That is another thing to consider with hard sided tents -- they take up the whole roof. You can decide whether that matters or not.
Live in the burbs' of Denver and will be using RTT in the mountains (rain/snow) but also for trips to Utah.
Of the tents that I have personal experience with, the Howling Moon is by far the warmest and the Columbus is probably the coldest. We've had the tent in pretty much every kind of weather except hail and have no complaints. Scratch that, the fly flaps and is noisy in wind. The Howling Moon fly is louder in breeze than Eezi Awn, but it also covers almost the whole tent, where the Eezi Awn covers the top. In Colorado, rain and snow generally fall horizontally, not vertically, so I will take the extra fly noise. It is pretty easy to remove if it bothers you. The Columbus has no fly to flap, unless you put on the winter hood.
The Howling Moon comes in a couple main styles (as does Eezi Awn) -- a regular tent and a "touring" model with an overhang that covers the ladder and an annex that you can zip on to it. I have never slept in a regular model, but most of the time I think I would prefer it. However, where the touring model is really nice is in inclement weather as it gives you a protected area to put shoes/clothes on and it keeps rain/snow/ice off the ladder. What I don't like about it is that it is more fabric to flap in the breeze, adds a few lb. to the tent and takes an extra minute or couple to set up.
If you go with the Howling Moon, one option I would strongly consider is their Stargazer option which adds skylights to the tent so in theory you can watch the stars as you drift off to sleep. I am way too blind for that so I've never tried it. However, the Howling Moon uses a very thick/dark canvas and the tent is dark as night even in the middle of the day. With the fly on and the skylights open, you have a nice, bright comfortable area to wait out a storm with your family. Any of the other tents that I have spent time in, the fabric is thin/bright enough for that not to be an issue. If you like to sleep late, the Howling Moon is worth consideration.
Eezi Awn and Howling Moon both make tents large enough to fit your whole family or small enough to mount two (one opening forward and one opening back), but not sure if you have enough roof area to do that. A 1.4m tent is a nice size for two, maybe go up to 1.8m for you and the kids, or 2.2m if you want everyone to fit comfortably in it for years to come.
There is an importer in Santa Fe and a few tents floating around town here if you want to check one out.
