Freestanding tents do not need stakes or guylines to remain upright. These are very stable and perform well in rocky or icy places. Newer clip designs have the tent walls attached to the poles with nylon fasteners. They're also easy to set up and take down, and are very good performers in anything but extreme conditions. But when heavy wind is bending your tent walls almost parallel to the ground, traditional sleeve tents are probably your best bet.
Capacity is subjective.
People experience spaces differently, and what is adequate room for some folks, is claustrophobic for others. There's also a big difference between sleeping in a tent for a few hours a night, versus waiting out a storm for several days with three young kids bouncing around. Weight is a great concern when backpacking. A tent that weighs a pound less than its competitor allows you to bring an extra pound of food on your trip. Lighter materials that are still strong and durable, though, tend to raise tent costs significantly.