The speed at which programs load will depend on many factors. Not the least of which is the version of the program that you are trying to load. But also depends on overall system load and available resources. If you believe that you are experiencing slower performance than you should, then try this: first thing in the morning (or any time after whihc you haven't been using your computer for a while) type "upitme" at the command prompt (sans quotes and see what the load average reports. Albeit unlikely, you could be running a good number of other high load services.
Also keep in mind that memory benefits Unix systems. 128 should be okay, though.
Finally, Netscape comes in several flavors. Mozilla (the open source project) loads significantly slower on my system than does an older version of Netscape (from
www.netscape.com). Could be code maturity, bloat, or just my platform.
Last note: if you aren't seeing a splash screen with Mozilla, then that could account for the extra seconds. On my machine I stare at a borderless splash screen for a couple of seconds before the main window comes up. Could be your window manager doesn't handle transient windows well.