The Vivoteks have Digital IO terminals.
So you can hook up the DO to a zone to alert the controller when a camera motion trips and hook the DI to a controller oeprated relay to signal the camera to turn on or start recording.
So if one camera trips you can use these inputs and outputs to signal other cameras to start recording, to turn on lights, etc.
Or you can use motion sensors or a driveway sensor to turn on lights and start recording.
The DIO really increases the effectiveness of the system.
I installed an Omni Pro II in an already finished 2 story house. It's a lot of cable pulling, like any alarm or controller, but doable. Thorough pre-planning made all the difference. I have 48 zones on the main board and a wireless receiver and a wired expansion enclosure, 3 T-stats, 7 smokes, 2 5.7e touchscreens, two-way audio, etc. I did it all myself.
I don't have any experience with ELK controllers, but they have a good reputation here. I'd say either one would serve your needs.
As I understand it Omni is initially more expensive, but comes with more standard functions. As you add Elk modules to add capabilities the prices seem to be on parity. AS I said I don't have any experience with Elk, but It appears to be a good system.
I use approximetely 95% SA products in my UPB install. I use just a few Western Mountain items and one or two HAI items. SA UPB operates perfectly with HAI. You have to use the HLC convention to get good ststus tracking. All that really is is a structured allocation of unit IDs to rooms and links. Once that is understood, programming is easy. HAI's website and this site have excellent info on HLC.