Which one of these systems would be easiest to program and configure
Your web page states "...phone systems (Nortel, Meridian, Avaya, etc.)."
I can only assume by the use of et cetera that you service other system but perhaps are not certified and thus cannot obtain technical support or new parts as an Authorized Dealer?
[
Personal Side Note: I have "serviced" many more systems than I have certifications for.]
If you cannot obtain Technical Support for the duration of your warranty period then it really reflects on your company.