Thanks jspeedy, what I have read and not found out first hand is:
S---stands for Safari X---stands for X-Terra 70(5)
=>The S is a slower sweep machine(like all FBS and BBS units). The X in Coin & Treasure Mode can cover much more ground in a day.
=>The S(like all FBS and BBS units) is much deeper 'wet' saltwater sand.
=>The X finds small gold(up to about 3/16" surface area--about 1 gram) much better than the S. I contacted Minelab, and that is why BBS and FBS machines are not recommended for gold prospecting as they are not as good at finding very small sub-gram nuggets as single frequency(being 18.75--20 kHz) machines are better at this. But for gold nuggets bigger than about 1 gram the BBS and FBS machines will work well.
=>The S(like all FBS and BBS units) has trouble with very small, very fine gold link chains. For normal sized bigger gold link chains the S does good on them.
=>The S(like all FBS and BBS units) has about the same depth as the X in black dirt and sod, but the S goes a little bit deeper in moderate mineralized soils and rocks, but the the goldfield heavy iron mineralization in Prospecting Mode the X does better than the S.
=>The S(like all FBS and BBS units) works a bit better in iron trash.
=>The S(like all FBS and BBS units) has a bit stronger discrimination than the X.
Most of these come down to FBS and BBS vs X-Terra 70(5).
(Very basically, as most all of you already know, the fixed-shaft Safari(FBS) has a TID screen, the hip-mountable Sovereign GT(BBS) does not. The E-Trac has a 2 number conductive--ferrous system, the Safari only has 1 number.)
Also this is what someone wrote about the X-Terra 70:
DEPTH
This detector goes as deep as the expensive models (Explorer Quattro Sovereign) in dry beach sand, all soils, but does not go nearly as deep in damp beach sand because of the salt effect. Especially when set in prospecting mode, it will easily pick up very fine jewelry and tiny nuggets that the others (Explorer Quattro Sovereign) won't even beep on. On the goldfield, it will detect deeper than any of the above, especially on small nuggets.
DISCRIMINATION
Is adequate for 99% of users. Only the Explorer series will discriminate better but the Xterra 70 is much simpler to use.
It has 3 discrimination modes or patterns that can be used factory pre-set or customized by the user to set their needs.
HANDLING
All the Xterra series may look light, small and unimpressive compared to their big Minelab brothers but thats what makes them a featherweight that any little lady or kid could swing for hours on end.
Hope this helps a bit, I have an X-Terra 70 and I have never operated a Safari, does anyone have anything else to add to this, no matter how brief ? Thanks!