Backpacking Tents Part 2: Intended Use
You first have to consider your intended use for a backpacking tent. Where will you be hiking most of the time, and in what weather? I know that's a simplistic question because you will probably want to go many different places and in all kinds of seasons. But first let me explain your options:
"3-season": suitable for the worst weather of spring, summer and fall
"convertibles": designed so you can leave out a pole or zip out a section or panel, converting four-season into three-season
"2-season": generally best for mild weather conditions; "ultralight" backpacking tents often fall into this category Minimalist shelters: may or may not be considered a "tent"
What's the difference then? 4-season backpacking tents often have more poles for strength (i.e., 3 or 4 instead of 2 or 3). They'll have very little if any mesh (bug netting), so as to hold in warmth and keep out wind. Other differences: large vestibules (explained on the next page) and/or tunnel entrances, often a more aerodynamic profile, multiple tie-downs, internal guy points, more adjustable vents, and so forth. Again, meant for the most severe weather. Many people like this security and versatility year-round, even if not necessary, and that's perfectly fine, but it comes at a cost: extra weight, and usually dollars as well.
The so-called "convertibles" can be handy. I have a Sierra Designs 4-season convertible tent where I can zip out the ceiling panel and leave home a pole to make it "3-season" (but I rarely do so). What I like most is the option of seeing the stars through the mesh ceiling. You don't necessarily need a convertible tent though: you could also simply leave home the rain fly if you're sure of no rain. Or, leave home the tent body if you're sure of no bugs and if your tent is designed to be pitched without the body.
Ultralight backpacking tents, or 2-season tents are best suited for mild weather. However, it depends on your experience, preference, and comfort limits. Ultra lightweight style backpackers could probably get by with minimal shelter in the extremes of all 3 seasons, because saving weight is the primary goal. Just keep in mind that this category of shelter can flatten under a fierce wind (I've seen it happen) or crumple under a big snow load.
If you're going out in warm weather or simply want to shave pounds, you may want to consider a inner tent consisting entirely of mesh (except for the floor). They're super lightweight and will keep out the bugs and allow maximum ventilation. With desert camping, though, if you expect lots of wind, you may want solid fabric walls to keep out gritty sand.
Among minimalist shelters, there's the "tarp tent", consisting of, you guessed it, a tarp (and some rope). A tarp tent is the ultimate in versatile, lightweight shelter, but you have to be good at rigging it up. It requires either hiking poles or at least one available tree. Done right, it can perform just fine in rain, but isn't good for shifting winds and won't keep bugs away.
Also in this category is the bivouac bag or "bivy sack". These are often packed by mountaineers as emergency shelters, but they can also be used for ultralight backpacking. They will, however, expose your head to the elements if you try to do anything but lie down with your head covered. So you can also choose from among the hybrid bivouac bags and one-person shelters that keep the minimalist, low-profile approach of a bivy but gives some sort of low overhead canopy using a small hoop or two.
Your intended use also helps determine other features, as well as what you will accept for capacity, weight, and cost. I'll discuss those next.
Next: Backpacking Tents Part 3: Important Features
Part 1: Backpacking Tents Intro | Part 2: Intended Use | Part 3: Important Features | Part 4: Capacity and Weight | Part 5: Conclusion