As far as I can see from what our 'murrican cousins have to say a proper table saw has a very rigid trunnion (or better still two) - the part of the saw used to tilt the arbor - whilst the site saw has a flimsier single trunnion and is generally of lighter build. A table saw is also integral with its cabinet rather than sitting on a fabricated base. I think that the site saw has pretty much been displaced (in the trades) by the flip-over/pull saw (Elu, Maffell, etc) and the sliding chop saw.
I suppose it all boils down to how heavy the workload is going to be - site saws were developed to allow trim carpenters, etc. to carry their saw to the job site in the back of a pickup whilst table saws are meant to be static and as such can be heavier and therefore more stable and accurate.
On this side of the big pond we break table saws down into three different type.
Bench top. Small, lightweight saw. Direct drive motor mounted directly under the table top. Table is small, and normally they have a short arbor. This means that Dado cuts are mostly limited to 1/2".These saws may or may not have thier own stands. Fence leaves alot to be desired.
These saws are a lot heavier than a bench top saw. They have Cast Iron tops. Lower priced units have stamped steel extension wings. The motor is normally 1 1/2 hp dual voltage, belt drive. It is mount in such a way that it hangs out the back of the saw. Contractors take this saw to job sites that they will be working at such as building a home.
Cabinet saw. This is the heavy weight saw. 3 hp, 220 volt triple belt drive. TEFC motor under the saw, so it takes up less space than a contractors, but is a bigger saw. Dust collection is great on these as the sit on an inclosed cabinet. Fence systems are good to great. Fence systems are 30" to 52" right of the blade, can have slidding table etc.
DeWalt and the Jet SS are being refered to as a Hybred saw, as the fall between the Cabinet and contractors saw.