www.owareusa.comI use their Cat 3 tarp, although I find it a bit short (or maybe I'm too tall) and I'd like to make my own. Some day...
One of the cool things about tarps is that you can change their pitch to accommodate different kinds of weather. Heavy gusts of wind and rain? Pitch it low and flat so that it doesn't catch any of the wind. This extends the sides outward, farther away from you, giving you plenty of protection from rain coming under the sides. And since it's lower and flatter it avoids wind loading, which in a tent could be a threat to the seems, zippers, and poles. So the tarp has a "robustness" advantage vs a tent, and the advantage increases the harder the wind blows. And being so simple, tarps are much easier to repair and jury-rig back into service in case they do break somehow. I had a corner tie-down loop pull out of an older tarp once, it was really easy to use a sheet-bend knot to tie it down and keep going. I've had tents fail on trips too, but I've never been able to fix one up in the field with any success.
Anyway, in calm weather you pitch a tarp high and tall and open, all you really need is to keep the dew fall off of your bag. That gives you lots of luxurious space for your sleeping bag, pack, boots, dirty clothes, cooking gear (if you're safe to keep it where you sleep), etc. The Oware Cat 3 is designed as a 3 person shelter, and it's palatial with just me under it.
Either way, you'll get much better ventilation and no moisture buildup in your sleeping bag. This is especially important in the rain, where a tent can keep you from getting soaked from rainwater, but can't keep you from getting wet from condensation from inside the tent. The higher the humidity, the more a tent-camper will accumulate dampness inside the tent and sleeping bag, and the colder he'll be. Even in a heavy rain a tarp allows enough cross ventilation to keep things mostly dry, and therefore much warmer. This is really apparent on trips when you're stuck in your sehlter for several days in a row due to weather. You can feel the dampness creep in and rob you of heat when you're stuck in a tent, but I've never experienced the same effect in a tarp.
I don't know if you've read Ray Jardine's backpacking book, but it gives lots of information on the advantages of tarps, how to pitch them, why they're better than tents, and even how to make a good, usable tarp out of hardware store sheet plastic. Definitely worth reading.