Both have been thoroughly tested and are known to work fine. You are encouraged to investigate both. VCON Escort 25 . This is the lowest-price system, and it contains some advanced features and options. It does not have very effective echo suppression so you will probably have to use a headset or an echo-canceling speakerphone.
Software updates are by paid subscription.
Zydacron Z340 . This is a higher-priced system, but it also has better video, user interface and control tools. Good echo suppression. Software updates are free. You can discuss with him various options, maintenance agreements, etc as you wish.