The differences you ask about are illustrated best in the white paper (first item) where the "old world vs. new world" perspective is outlined. Most of the ones you mention are "old world" insofar as they are largely device-centric and typically are high maintenance. Many of our customers report shelving their expensive investments in these products, citing (in at least one case referring to OpenView) the need for 3 full-time employees just to maintain the network management system.
As some of the other answers point out, your first question should really be, "What do I need and what can I do without?" Solutions range from free (Nagios) to really expensive. And effort ranges from very low to unreasonably high. And then there are the feature sets.
From your list of NMS considerations, it sounds like you have
If any of these guesses is inaccurate, then you should review the white paper's criteria and identify your needs. I will stop short of a comparative analysis of each of these NMS candidates pending more clarity on your situation.
This was first published in September 2004