Not a good understanding. They're both available for anyone to see.
Photostash was the original offering. It has a heavy size restriction to avoid overwhelming the VRCC site. Just Pics was brought on later in part to alleviate some of the complaints about file size restriction.
Honestly, if you're just going to store pictures on the web you'll be better served by using Photobucket or some other site that has a primary function of providing a place to store pictures.
I actually just use photo bucket. Not sure how the pictures in photo stash are available to everyone when my own aren't available to me unless I can remember that password (sometimes I can and sometimes I can't) haven't tried in over a year. Just pics however is just a tab on the homepage. But, oh well that's just my experience.
