Consider these things as you select a tent:

Marketing

1. a 3-man tent is barely large enough to hold 3 sleeping bags.
2. a vestibule may be useful for storing dirty items, but not for protecting anything from animals.
3. any tent that promotes using the vestibule for cooking in the rain should be disqualified; they're not looking for repeat business.
4. odd looking floor plans can actually be useful.
5. inside pockets are to make things easier to find, not to keep them from getting wet.

Walls

1. Single

+ weighs less
-  touch-and-leak feature
-  may lack a floor
2. Double

+ can be carried by two people
+ if freestanding, is good for rocky areas and concrete surfaces
+ can provide good ventilation
+ allows mesh windows and doors, plus rain protection -  is a bit heavier
-  is a bit more expensive

Space

1. sleeping
2. storing equipment
3. changing clothes
4. sitting and reading in bad weather

Other features

1. short pole sections are easier to pack
2. insect protection from no-see-um screen mesh
3. bathtub bottom for low areas
4. a separate ground tarp or sheet to protect bottom
5. double-ended door zippers
6. doors on both ends for better ventilation and exit options
7. shockcorded poles (easier to put together and harder to loose parts of). Now if they can only figure out how to use shockcord on all the tent stakes.
8. a dome tent, with nearly vertical walls, has more useable space than a tent with more slanted walls.