how do the standard edition liveCD and installer CD differ?
 

On the VectorLinux site, for the standard edition, there is an "installable disk" edition and a separate liveCD edition. This is the first distro I've encountered with an edition that installs the distro but is not a liveCD. The site says they have the same features, and from trying both, I know they're both installable. (I've never seen a liveCD that isn't.)

So, why might I want to install using the "installer" CD when I could install using the liveCD?

Not quite sure about Vector, but in general the method of installation differs between live-media and installer-media. Usually live-media make a copy of the live-filesystem to the harddisk (and make necessary changes to the configuration afterwards), while installer-media install the system using packages. Both methods have done and upsides: While copying the file-system is in general a very fast way to install a system the problem here is that you have a pre-configured system, while the package-based approach of installer-media is in general slower, but gives you much more flexibility, for example with changing the installed packages before the install or using network based installation methods with always up-to-date or custom compiled packages.

So, if you want to make a fast standard installation of your distribution the live-media approach is usually preferable, while the installer-media solution is better for customized installations. For example, back in my Debian times I used the net-install medium to just install a base-system and then I used a pre-configured package-list together with a local package cache to complete the installation. This way my installation contained exactly the packages I wanted, in the newest version and an installation never took longer than half an hour, configuring the system to my needs inclusive. I could have taken the time to create a custom live-medium for the same installation, but this would soon lead to outdated packages that have to be updated after the installation.

Thank you. I don't have much experience with making customized installations: I've tried Debian proper before but almost all my experience is with distros that offer only a liveCD for installation; and it works for me, so I guess I'll stick with the Vector liveCD. As you indicate (subject to my interpretation), the liveCD distros just dump themselves onto my hard drive, and I sort them out after installation. Aside from whether I want a fast and standardized installation (generally, I do), customizing after installation seems to me no better or worse than customizing during installation.

Which one you prefer is just a matter of taste if you don't have the need for customized distribution. Back in the days I always started with a minimal install of a distribution and just added the packages I needed, just because this makes more sense to me on distributions with dependency resolution (infamous metapackage problem) and because my hardware resources (at least in the first time) were rather limited.
Nowadays I use Slackware and since harddisk space is cheap I just don't care anymore, use the default installation and only add some packages that are not part of the default installation. Ripping out parts of the installation for a few MB on the disk just doesn't make sense to me anymore.