Solid conductor cable is meant for static installation (like "in-the-wall") Because the conductor is solid, it doesn't tolerate repeated flexion.
Stranded conductor is meant for jumper cables (like from the wall-plate to the computer). Because the conductor is stranded it does tolerate flexion and a little more stretching force than solid.
Solid conductor has better transmission characteristics (like less loss). The "100 Meter rule" for Category-rated UTP is based on 90 meters being solid conductor cable with 5 meters at each end being stranded (jumpers).
"Shielded UTP" translates to "Shielded Unshielded Twisted Pair" To make it less confusing, when shileding is added to UTP it's called "Screened" UTP.
There isn't much in the way of Category 5 Shileded cable (screened UTP or Shielded Twisted Pair). Belden and IBM came up with some, and a new type of connector, to replace the "Type 1,6 &9" cables and Token-Ring-style connector. It was rated at what is now Cat 6, but it never really caught on (dead now, I think).
Improperly terminated shielded twisted pair (or sUTP) can cause more problems that it was meant to solve (i.e., gorund loops, noise collection and radiation, etc).
So far, the cable manufacturers have been able to improve performance with new insulative compounds and twist formulas (not all pair in the same cable are at the same twist count per foot, every manufacturer's twist rates are different). There was a minor stutter in the progress a few years ago when CFCs were banned; manufacturers had to come up with a suitable replacement for wire jacketing because the "teflon" stuff they were using was part of the ban.
Not all UTP is category rated. "Regular Phone Wire" is totally unrated (usually not even making Cat 3 level certification).
All components (Cable, connectors, panels, punch-down blocks, data outlets) have to match for the cable to be "Cat X" rated. I.e., to have a "Cat 5" rated connection from one computer to another, the connectors, cable, outlets, panels, and punch-downs (or whatever subset) all have to be specifically rated at Category 5. If any of those components are at Cat 3, then the entire system rates-out at Cat 3.
Another complication to Category-Level certification is installation. If the cable gets kinked, severly twisted, stretched, or crushed...it may be out-of-spec. If the connectors are not terminated properly (more than 1/2 inch exposed and/or untwisted), it's probably out-of-spec. If there's a bend in the cable less than 2" in diameter, the cable is out-of-spec. If there are more than two intermediate connections, then the cable isout of spec. If the total length "in the wall" is longer than 90 meters (~270 feet), the cable is out of spec.
Coax is still a better data transmission cable, but the topologys that use coax tend so suck beyond budget and maintenance tolerances.
Fiber still beats both, and EXCEPT for a 3M product (Volition...something like that) that makes fiber about as cheap & easy as UTP, most fiber requires fairly expensive tool kits (US$1000-2500) and skills for termination, and the components (connectors @ US$5-12) are much more expensive.
Anixter has been putting together a "Levels" program for Fiber for the last year or so to rate performance of (I believe) multimode fiber. Anixter "Levels" program for copper was the basis for the "Category" rating system now in use....so someday you may see "Categoty 11" rated fiber.
I hope this was helpful......
Good Luck, happy holidays...
Scott