It does matter actually. You're assuming the system will get destroyed after it's activated. If an intruder enters through a zone that's programmed as an entry/exit zone they'll have at a minimum of 30 seconds to destroy the main panel which is plenty of time.
Not true. You seem to be speaking from the perspective of someone either has no alarm, or has only had very low end consumer grade systems. Delays can be set from zero to in excess of 40 seconds in 5 second increments on my typical system. There are 3 factors here:
1. Where you locate the AIO panel - next to the main entry door is an idiots positioning - you want any burglar to waste time looking for it.
2. How long you set the delay - you want it so short you barely have time to reach the panel at a rush and get the code in. Mine is under 20 seconds and it takes at least 12 of those seconds to open doors and get to the panel from the main entry point at a rush when you know exactly where the panel is, leaving just 8 seconds to enter the code. There's not time to correct a mistake.
3. You should be setting individual delays for each Zone not a one size fits all delay, and on a full arming, given no-one will be in the property, for any Zone other than the Main Entry Point ie the door you usually exit / enter the property by, the delay should be zero resulting in an instantaneous trigger.
That's also assuming the system is using a modern form of communication such as IP or Cellular. If the system is using a phone line, it'll take an additional 15 to 20 seconds on top of the 30 second entry delay for the panel to pick up the line, dial the central stations phone number, and transmit the alarm. Furthermore, you're also assuming that the OP will protect every entry point and the alarm will activate as soon as the intruder breaches the perimeter. Fact is most people don't protect every entry point (Door/windows) and could tamper with the unit before the alarm is even activated.
In addition, the OP stated he does not want a monthly monitoring fee. Using an AIO system will eliminate the ability to use 3rd party communicators like the Envisalink 4. This would result in the OP having to sign up for either basic self-monitoring using an Interactive service or having the system as a local alarm only. The only AIO system that I'm aware of that allowed an end user to program a cell phone number into the system to get notifications upon an alarm is no longer produced.
A monitored alarm will trigger instantly locally irrespective of whether it also dials a monitoring station unless it's a silent alarm, and typically, only panic buttons tend to trigger silent alarms and then only on some systems. Most systems use a non silent panic.
Any householder that doesn't cover every room downstairs is an idiot. It's true to say you probably can't afford to put a glass break sensor on every window, unless well healed. However, a single well positioned PIR sensor will cover an entire room and all entry points for the cost of the 1 unit. The minimum fitted in my opinion, should be 1 reed sensor on every external door, that's usually 2-3 total, and a PIR on every room covering all entry points downstairs, usually around 3-4 for a typical house, depending on the panel mounting location. Larger houses may need more, but if you have a very large house, I doubt an extra PIR will break the bank. Additionally, a minimum upstairs should be a PIR covering any common area such as a landing and a glass sensor on any easily accessible window ie those that can be reached from roofs or next to drain pipes.
As IAmaTeaf mentioned above, your perception of destroying the panel is also incorrect as most decent bells have electronic logic boards built in and these alarm if the panel signal is removed.
Additionally, my panel communicates wirelessly with the bell, and has tamper switches fitted that detect front panel removal. Hit it with a hammer and flex or smash the case, and it will send a trigger system when the case flexes or is broken and the tamper switch activated as a result. Electricity travels faster than a hammer head and even if it didn't, again the fact is the bell will sound if the panel signal is lost. Again this is why panels have back up batteries fitted - so they don't cause a false alarm and go down if the mains goes down.
My panel is no longer produced, although I think it's replacement model is the same, does telecommunication - mine uses the normal phone line to contact a monitoring centre if you subscribe (I don't) or can be fitted with an optional SIM card module to use cellular if the phone lines are cut. In my case, not paying for monitoring, means it phones my mobile if triggered. Not many panels do this true, but then again you have a choice and a price point and telecommunication is not essential.
