1. IPC
2. BT
3. OBS orange business services (Etrali)
4. IP Trade
5. Siemens trading
6. Speakerbus
That is the order of sales/installs.
1. IPC are a good reliable system with good integration
2. BT reliable but tend to copy technology from others (sometimes improving it though)
3. OBS very good product especially the new open trade system
4. IP Trade awful, really awful, can't describe how awful they are.
5. Siemens new design, very little investment, small support footprint.
6. Speakerbus don't know anything about them.
Biglebowskis Razor - with all things being equal if you still can't find the answer have a shave and go down the pub.