Just my twopence worth - I have installed Scantronic, ADE, Ademco Galaxy over the years, both hard wired and wireless. I don't personally agree with the bad spec given here to Scannys - generally found them to be well built panels with a lower than average failure rate.
If you are aiming mainly for the "bells only" market with no monitoring, most of the main panels on the market will do you fine. My advice is to stick to two, max three makes and get to know them well - it's half the battle when you can programme, reprogramme etc without having to constantly refer to the installation manual. I also pay a bit of a premium for external sounders - after all they are out there in all weathers.
Domestic/small commercial intruder systems is approx 25% of my turnover, with access growing from 10% - I get very little hassle from my own installations and a reasonable margin. It's like the thread on today about satellite installation - you can never have too many strings to your bow, but play them all competently!
Regards.