Just quick review of features that "good to have" when you choose surveillance system.
1. Sure your budget. There are a lot of big players who will be more then happy to take your money. But careful, money spoiled many of them, their software very heavy, complex and often useless. Service probably great ;)
a) Multiple user support
b) Support user roles
d) Web interface
f) support for many manufacturers, not just support but support of camera features. It is really sad if you have 2K PTZ camera that you can't use as PTZ
j) Flexible camera layouts. More is better
k) Algorithms for image recognition. more is better
l) Support handheld devices.
m) Camera assessment. What is this? Simple, camera can follow the object and pass it to another camera if object leave camera vision area. Nice feature, I like it.
But most important simplicity and price. That is it, now go and choose one that you like.
BTW we can't implement reliable assessment with simple IP Cam, but other points we do. And our system completely free ;) Will release it soon, stay tuned