Greetings Josh,
The "nolib" version of addons (often referred to as "running with disembedded or standalone libraries"), as you have already mentioned helps save a bit of disk space, depending on the number of addons you are using. Considering the fact however, that modern hard drives come with an abysmal size out-of-the-box, when compared to the few kilobytes that you are saving, the real "benefit" is really up to you to discover.
Other than that, it has been often iterated that disembedded libraries help decrease loading times (imagine a few seconds though this may vary if you are using more than let's say 40-50 unique addons with embedded libs), which is true to a certain extend, since no real version comparison occurs between libraries that are being embedded by multiple addons (note that when a library is being used by more than one addon, only one copy eventually stays in memory, the most recent version that is, the rest are garbage collected by WoW the first time the collector is run by the client). While this used to present a sort of an issue in the past, with a few libraries getting bloated by features that were only used by a couple of addons out there, the introduction of relatively lightweight frameworks such as Ace3 has remedied this, significantly.
All in all, you really shouldn't need to worry about disembedding. Just use the addons the way their author(s) intended them to be used. Disembedding was really meant to be used by authors and power users, for CPU/Memory profiling purposes (for the most part), since it is the only reliable way to "measure" the resources being used purely by the addon.
I hope this helps
P.S : Ace is not an acronym
