I mostly use memorize for temporary activities and saving to the library for more complete efforts. Memorize is a fast save and saving to the library involves writing a new file and takes a little longer. It's that time difference that makes memorize more useful. Saving to library saves all figure and prop information so that it loads everything the next time Poser is started. Memorize only saves parameters for that session of Poser and it's lost after that. Memorized settings can be activated with keyboard shortcuts opening a library items loads something new into the image.

The most powerful feature for memorizing is that saving to the library will save the memorized settings as default settings. Let's say that you've morphed a figure exactly the way you want and that figure will be used over and over. Saving that figure to the library will save the figure with all the morphs, but will not save that figure to a default state with the morphs. Using a restore action on that figure will revert to the figure's default factory loaded state.  By memorizing the figure first, and then saving to library, a restore will only reset changes made since the figure was loaded, but will not get rid of the morphs that had been saved. Resized/repositioned props, hair, imported files, etc. will retain whatever changes had been made to the saved version. This is very useful for a figure that has a lot of resized, repositioned, and parented props.

There are a few other areas where I use memorize. 

• Morphing and posing a figure. Memorizing a morphed figure saves that morph as the default when "restore" is used. When I'm doing things that are going the wrong way and it's no longer easy to get back to an earlier state,  I'll hit SHIFT-CTRL-F to reset the figure back to it's default state. Without using memorize first, that default will be the default figure's appearance and not the version that I morphed to.

• Setting a hair prop element to stay with a morphed figure. If a restore operation is made to a figure that is using hair, that has been resized or repositioned to fit on the figure, the parented hair also gets restored to its default state and no longer fit or even be on the figure that it was modifed to fit. Memorizing the hair fixes that problem. Performing a restore on the figure doesn't move the hair anymore.

• Temporary lighting or camera settings. If I'm kind of happy with the lighting or camera angle I've picked, but not quite ready to save to the library, memorize will let me store those settings so that I can hit some keyboard shortcuts to quickly get back to them. Most of the time, I'll use camera dots for that purpose, but there aren't any memory dots for lights.

My visual indexes of Poser content are at http://www.sharecg.com/pf/rgagnon