On new construction, I use T flashing on the edges, then 30 pound paper and architectural 30 year shingles. Then I use 1 5/8 inch nails. The 30 pound paper costs the exact same amount as the 15 paper, but you get half as much. This is the one thing that I really force on my clients. Don't try to save a buck on the paper, it's the most important part of the roof. Then while the 3 tab shingles will get the job done, and I use them if I'm matching a roof or the client insists on using them, I don't like them and would never buy them for myself. They are rated for 20 years, which is cutting it close. I was at a house yesterday with three tab shingles on it that was built 7 years ago. While they were not leaking, a few of them were already starting to curl up. Loosing rock and then curling up is a good sign that they are at the end of their lifespan. They have another five years easy out of that roof, but it's already started to go on them after just 7 years. The architectural shingles cost quite a bit more money, but are also allot heavier and thicker. They have a 30 year warrenty and from what I've seen, they hold up really well their entire life. I don't come across architectural shingles that are curling up and loosing rock like I do three tabs. I can't even think of an example where I've seen them failing from just age and the elements like I can with 3 tab shingles. The other thing is how they are installed. It's faster and cheaper to use staples. The problem with staples is the gun has to be ajusted just right and the installer has to really be paying attention to what he's doing. The problem that I see over and over again is that the staple went into the shingle too far and broke through the shingle. When this happens, it's lost it's ability to hold the shingle in place. A staple has to be snug on the shingle to do the job. When done properly, they work great, but on an entire roof, it's never 100 percent. Short 1 inch nails are another problem that I've run into. They are not long enough to fully penetrate the roof decking. If the shank of the nail isn't through the wood, then the nail will come out real easy. I like the 1 5/8 nails because it goes all the way through the wood and holds tight. While the short nails are cheaper and allow the roofer to make a few bucks more profit, they fail all the time in high winds. Comparing staples to nails, it's allot easier to see if the gun shoots a nail too far into a shingle then a staple and add another nail when it happens. I know of one roofer in the area that hand nails his roofs. He's becoming very popular because of how well this works, and clients are willing to pay a bit extra to get it right. While 90 percent of leaks that I come across on roofs are flashing issues, the other ten percent are from nails, shingles and branches or other objects that have put a hole in the roof.
Anyway, that's my oppinion on shingles.
Eddie