If you don't know which browser to choose, then let me help you.
The obvious differences are actually quite simple:

Microsoft Internet Explorer is faster (4.x)
Netscape Navigator has a nicer interface.

If that's not enough, check out this list:

Microsoft Internet Explorer
Knows the code <Marquee>, which makes text slide across the screen.
Also knows the code <Bgsound>, which plays a background sound.
Knows the code <Iframe>, which is used to make internal (floating) frames.
Faster at loading a page except with resized pictures.
Faster with Java and JavaScript.
When reloading, IE only reloads the changes, where Netscape reloads the whole page every time, this makes IE faster at reloading.

Netscape Navigator
Netscape is faster with resized pictures.
Knows the code <Blink>, which funny enough, makes text blink.
Knows the code <Spacer>, which makes a certain amount of space between objects.
Netscape has a nicer interface (especially with 4.0)

The best thing is, you don't have to worry about money, they're both FREE.

If you're using Microsoft Internet Explorer, this text should be scrolling. If you're using Netscape Navigator, it should just be normal text.