IP Office
Advantages
IP Office will likely be cheaper
IPO will integrate efficiently with other Avaya platforms such as the S87xx this is also usefull.
IPO offers a wide range of robust telecom applications not commonly found in cheaper devices. Not the least of which is a powerful conferencing application (40+ parties) when coupled with VM pro.
Disadvantages
IPO does not require a network asessment because it is a stand alone box not requiring any call control from a master.
Completely different programming and administration skills required. IPO uses ASCII and a GUI to Administer the system while it is not that difficult to use it is vastly different then ACM and will require you to learn a second set of admin commands etc
Gateways (250,350,650,700, MCC et al)
Disadvantages
A gateway either survivable or not will likely cost more
so I guess that is a disadvantage.
A gateway will likely require a network assessment and changes to your network to allow for QOS, VLANS etc.
Advantages
Gateway will integrate cleanly with full feature sets (FACs will be uniform etc).
Gateway can take advantage of your existing license pool at the main location (i.e. depending on your config you may not need to purchase more licensing).
Gateway will also provide you with the same programming platform you are used to whereas the IPO uses an Ascii type administration with some GUI elements.
Gateways of some types can use existing circuit packs so if you have spare DS1 or line cards you might be able to use them instead of buying new.
Gateways can offer multiple points of failure. It is quite possible to have a gateway re-register with another Master server in the event of an outage to that main cluster. So in a multi-site configuration it is common to have many tiers of redundancy.
That is some of the more obvious items...I hope it helps.
