Was in the buisness for a long time. With all the big national guys, ADT, Protection One, Brinks, etc. they are more interested in getting you to sign a multi-year contract than installing the best system for you.
They install "free basic packages" with an add-on or two and charge a lot for the add-ons. A good company will come in and custom design a system for your home.
Look for a local company that's been around for a while.
Hardwired is infinately better than wireless.
If you purchase a system outright you pay more up front, but should be able to get monitoring for $20 or less, versus $35 in monthly contract payment.
With the big guys you never own the system, they can, and do, raise your rates, and you have limited options as the contracts renew for like terms, usually 3 years, and your equipment is proprietary to them, only they can monitor it. With smaller local guys, if you buy the system outright and are ever dissatisfied with monitoring, any other company can monitor it.
The company I worked for still monitors for $180/yr., or $15/mo.
A good system will have all doors covered, a keypad at your main entry, and one in the master bdrm. You should have an inside and outside siren. If you're more worried when away than when you're home, motion detectors are ok, but they are the most prone to false alarms. Spiders crawl over the lens, alarm. They make supposedly pet proof ones now, but they aren't perfect and some municipalities now charge very high fees for false alarm dispatches. If you have good solid windows that are not easy to pry open from outside, glass break detectors are good. Contacts on widows are good too, as they let you know if you've left a window open, or if someone pries it open. Most companies don't like doing all the windows as it is labor intensive. And again, the big guys want in and out as quickly as possible. That's why they use wireless equipment. Screw it in the wall, put a battery in, and you're done. Fast, but not good.
What most people don't understand about monitoring is that your alarm simply dials the central station to send a signal, just like you calling someone. If the phone line is down, no signal can be sent. Phone lines are very easily disabled. It's exposed so can be cut, or more easily unpluged at the service box. There are celluar back-up systems if you're serious about your security. They are a couple hundred $$ add-on and usually another $15/mo for airtime, even if not used.
Generally a decent system will be close to $2,000, depending on size of house. Can be much more if doing all the windows, adding smoke detectors, etc. Smoke detectors are a must if you're getting a system. It usually doubles the discount you get on your homeowners premiums, (paying for themselves over time), and nothing beats a smoke detector that calls the fire department if you're not home.
Let me know if you have more Q's.
Brian