Hey Don,
Typically the strong safety has more value in balanced and tackle-heavy scoring systems as their role generally has them closer to the line of scrimmage and they consequently make more tackles. However, there are several teams in the league that play their safeties in the same capacity/role.
When in doubt, typically go with the SS or look back at the history of the two positions in that defense and see which was has produced better.
For sleepers, I have a free article on the site that lists out my thoughts. It's a bit outdated but still mainly relevant. It can be found here:
http://www.idpguru.com/2016/06/2016-idp-rankings-sleepers-redraft.htmlYou also have my draft guide which has everything you need to dominate the IDP side of drafts. It's $5.99. More information can be found here:
http://www.idpguru.com/p/2016-ff-draft-guide-purchase.html