Cesar its not just the sloped sides, its the single pole.

You can knock a lot of snow off from inside and press the snow outwards if you wake up often enough.

My buddy always got up and shoveled the snow from around his tent, sometimes several times in the night. Since he had a three hoop winter tent I thought he was being way too careful. Shoveling can damage the tent.

There are two alternatives to shoveling:
1) is to ignore it if you have a strong winter dome like my TNF mtn24. I shared it with a friend in a blizzard and there was a 3 foot high snow drift on top of it in the morning, but the dome shape - refer to the Roman arches supporting aqueducts - seemed to carry the weight around the tent and the outer tent was not pressed tightly against the inner tent, at least not enough to affect condensation as we were completely dry inside in the morning.
2) is to put your back against one wall and press the other wall outward with your feet, while remaining inside your sleeping bag. By pressing the snow outwards you effectively build a snow cave/wall around your tent which may help prevent the build up of deep loose snow that can collapse your tent. I've done this in my bibler and though the tent was completely buried, it stopped collapsing inward after about the third time I pushed it out.

A tent covered with snow is a lot quieter and offers a better nights sleep than one that flaps. This may be the best reason to carry a three to four pole tent, especially a dome.
Jim