A good quality deadbolt is important, but there is another factor to look at to ensure security.
Back in July, some A-hole kicked my front door in in the middle of the night...about 3:45 or so. Deadbolt and knob were both locked. The force of the kick ripped the bolt right through the framing around the door. The trim molding exploded. A piece of the door frame flew across the room with such force that it punched a hole in the drywall on the other side of the room. The good news is that all he wanted to do was scare us...which he was very effective at doing. No one was hurt and nothing was stolen. My wife and I didn't sleep too well for quite a while after that, and we still have a rough night now and then (last night was one).
The total to have the door replaced was just over $1200. Included in that was a very reasonable price of $60 to have a steel reinforcing plate mounted in the door frame. The plate is 1/8" thick, about 3" wide and runs the entire height of the door. There are 8 3" screws that run through the door frame, through the plate, and into the wall stud. The plate is drilled and the bolt engages through the plate when locked. The strike plate around the deadbolt also has 2 3" screws that run through the plate. Basically, if someone wants to give it another try to kick our door in, they'll have to bend the door in half...which of course can be done, but by the time they put enough kicks in to accomplish that, I'll be waiting on the other side with the other purchase that I made following the first invasion...my HK USP.
It was a terrible night, but we learned a lot from the experience. We made plans, discussed scenarios, practiced, equipped, practiced some more. My wife finally realized that the police AREN'T going to be there to protect us if something happens. (It's not their fault, they are limited to a reaction)
I guess what I'm trying to say is this...the lock is important, but make sure that the bolt is engaging through something worthwhile. Wood splinters way too easily, there has to be some reinforcement...and even that is no guarantee, so make sure that you've taken the appropriate measures, planned, practiced, etc.
Thanks for reading...
Mark