Ok, I'll start. I could make a huge post about this, but I'll do one thing at a time.
QREBS! I know, not a great name at first, but it makes sense once you get to know it. One thing that always bugged me about Traveller (never used FF&S so I don't know about that) was that in this huge universe of planets, cultures, tech levels, and alien beings, pretty much all equipment was the same. If you buy an auto-rifle, it's pretty much the same everywhere, unless your Ref goes and does some from-scratch work to customize it. (MT Equipment Sheets helped with this a little, giving different TLs differences.) For instance, we all know that Naasirka produces cheaply made, mass-produced consumer electronics, while Makhidkarun (did I spell that right?) makes state of the art stuff, pushing TL boundaries, but how to reflect that in-game if I buy a hand-computer? And what about the infamous Vargr-made (stolen?) goods?
Now that problem is solved with QREBS, a multi-scalar stat system for denoting various individual traits of any object, from a toothbrush to a starship. The scales are: Quality, Reliability, Ease-Of-Use, Bulk/Burden, and Safety (now you get the name). So for instance, a Naasirka P-100 hand computer may have a QREBS value that is average across the board, while the Makhidkarun XTC-9000 has a higher Quality, Reliability, and Ease of Use. So here we can reflect the differences in different models (likely affecting their price, but so far there is no hard rules for that, unfortunately. Exception: See TL Stage Effects). But it can also be used to reflect differences in individual copies of the same model too. Say, my friend's brand new P-100 has factory QREBS stats, guaranteed or your money back. Meanwhile, I got mine from Ebay-Deneb, for a fraction of the price since it's used, buts its QREBS suffer: Having seen action in the Fifth Frontier War, it's been damaged and repaired in the field a few times (Quality -1), the screen is cracked and has a funny splotch on the side that obscures some of the image/text (EOU -2), and the MMC-sized memory chip was fried, and jury-rigged with an external Compact-Flash drive (Bulk +2), and some of the wiring is exposed (Safety -3). But I got it for just Cr10!
TL Stage Effects just show the effects on QREBS (and mass and price, sometimes other relevant things) when an object of a certain TL is produced at a higher TL. Now an Advanced TL 14 J-2 drive is way better than the TL 11 normal J-2s, and certain better than the prototypes they were playing with at TL 9.
And to show how versitile these rules are, I've already created some house rules (with a little help from others) on how to use QREBS for art pieces, from pictures, music, movies, books, fashion, etc.!