A great list from Jexy.
I'd suggest printing it on paper, if possible, to make all that data easier to read.
I'd like to add a few points.
Simon has it down to two makes only, Carrera and Scalextric, so I am going to ignore the others for simplicity.
Although Jexy had difficulty in locating individual Carrera track pieces, they CAN be found and a pack of 4 Carrera straights is about £22, making it around 25% more expensive than Scalextric (depending where you price it, as always!) However the Carrera SETS, though not as common as Scalextric, are readily available and are very comparably priced.
The steel used in Carrera track is stainless and will not corrode over time like Scalextric - a definite plus.
Conversely, Carrera's stainless steel is not as magnetic as Scalextric - could be deemed good or bad, depending on personal preference.
Carrera track has a plastic groove separating the metal rails from each other, which may be considered a small protection from electrical shorts. Scalextric doesn't.
Carrera curve radius is greater than Scalextric
Carrera track is approximately 2 inches/50mm wider than Scalextric
Take these two factors together and Carrera needs a good deal more space for a given layout.
Depending on your space, this COULD BE the single deciding factor, completely regardless of any other consideration! Do think ahead about space.
Although Carrera track users rate it as the Rolls Royce of plastic tracks and it undeniably has some definite advantages that justify the description, it must be said that it is not as readily available as Scalextric, costs more as individual pieces, needs more space, being harder plastic makes it a little more prone to breakage (but less prone to warping) and is more fiddly to assemble.
So do think carefully before making the big decision.
I'd be VERY interested to know how many, if any, of our members are regular Carrera track users.