I don’t claim to be a WordPress guru by any means, but I have some experience with it and the caching plug-ins.
There is a really good description of the differences between wp-cache and super-cache on the WP Super-cache website, as well as a “short version” of the differences from WP developer Donncha on the WP support forums.
To my way of thinking, either is better than nothing, and which you choose depends on personal preference and the end results you are looking to achieve.
Note that wp-super-cache is a fork of wp-cache, and adds additional features.
I’d summarize it up by saying the wp-cache saves hits to the database (which is often the most significant cause of slow loading pages), but still uses PHP to render the page while super-cache actually serves static HTML pages (which saves not only the database interaction, but also the PHP loading/processing time.)
This difference can be significant on a host like DreamHost where PHP is running as PHP-CGI. There are other differences indicated for developers, but I have not really explored those; I’ve only looked at it from a user’s standpoint.