Rusty,

A number considerations come into play. Some of our rules of thumb are as follows:

A one-walled tent can be much lighter than a conventional two-walled tent (counting the rain fly). It will also be less versatile. The single wall must be a compromise between being water-repellent and airy. On a double-walled tent, the rain fly can be made very impervious to rain, whereas the main wall can be relatively porous for good ventilation. But then sometimes light weight trumps protection. In evaluating the weight of a tent, divide it by the number of people who will use it since the weight of the tent or its equivalent can be borne by all.

Check the size of the tent for yourself. Manufacturers ridiculously exaggerate the number of people who can fit in a tent. Consider your own dimensions in evaluating the actual roominess/snugness of a tent. Many products do not realistically take into account the real sizes of people.

The more the rain fly covers the tent, the more likely the tent is to be waterproof.

A floor which attaches to the walls on the sides (a bathtub design) rather than at the corners will be much more waterproof.

Be sure the tent allow for good ventilation even with the rain fly deployed. Otherwise, you may feel you are drowning in the humidity.

Look for a design that allows excellent ventilation, and preferably cross-ventilation to provide comfort in hot and balmy weather.

If possible, try to find a store where you can actually see the tents that interest you. Don't just rely on a catalog description or the manufacturer's specs.

Ask about the tent's wind resistance.

Finally, think how you will put up the tent. Some designs make it easy and quick. Others seem to call for party of mechanical engineers in a wind-free warehouse with unlimited time.

Incidentally, we just had the same quest. But we were looking for tent to be backpacked which would be comfortable for 2 large people (6'2" x 200#) and some equipment (e.g., rifles) even for prolonged periods. We ended up getting a convertible 3 to 4 season tent. It has ample ventilation to be comfortable in hot weather without the fly (and hopefully in rain storms as well with the fly). It will also see some cold winter use. It appears to have sufficient integrity for windy and rainy conditions. We have previously had significant problems in wind, rain, and hot weather. We ended up getting the Sierra Designs Alpha. It appeared to be the best fit our needs, however we haven't been able to try it out yet. We'll see.

Good luck on finding one that fits your own individual needs,

John