Big tarps have big footprints and are extremely unstable in high wind situations unless you stake all sides to the ground, which means zero headroom unless you have a pyramid style tarps. Also, staking all sides to the ground causes bad condensation regardless of the tarp shape.
A small tarp (such as oware 1.1 or 1.5) combined with a waterproof bivy is a good solution for cold conditions. My camping season runs from April through September, meaning much of the time is in the heat of summer, when a waterproof bivy is way too warm. So the solution I came up with is to use a Oware 1.5 tarp with an added back panel, to keep rain from blowing in from the rear, plus a raincoat or poncho hanging from an added loop on the underside of the ridgeseam, to keep rain from blowing in the front, with a home-made netting bug-bivy underneath. (http://www.geocities.com/frhiking/sewing_bugbivy.htm)
Assuming I pitch the tarp with the sides and back about 3" from the ground, there is still plenty of airflow due to the gap between the raincoat and the sides of the tarp. Yet I am still well protected from rain spray even under stormy conditions. This is because the loop for the raincoat is about 6" back from the front of the tarp so that the tarp overhangs the raincoat at the front, thus providing protection from diagonally blowing rain. Diagonally blowing rain can still enter between the raincoat and the tarp, but it will hit the sides of the tarp rather than hitting me.
I don't much care for the doors on the Spinshelter or the Integral designs Silshelter since these are something of a nuisance to close. By contrast, I can secure my raincoat/front door in place by simply putting a few water bottles or other heavy items on top of the lower part. It is also possible to tie the lower corners of the raincoat/poncho to the corner tarp stakes, in case a strong wind starts blowing against the front of the tarp, though I have never bothered with this in the field.
I have no experience with using a tarp/bivy in heavy snow with considerable spindrift. I'd probably use a tent if I expected these sorts of conditions.
I will probably be replacing my Oware 1.5 tarp with a slightly smaller hand-made tarp for next hiking season, since I find the Oware 1.5 is a bit too wide, especially in the foot area. There were a number of occasions this past hiking season when I was trying to camp in spots hidden away in the bushes, and the large size of my tarp was a problem. Otherwise, though, I can highly the Oware tarps.