At this point, it's best to decide on one make and stick to it. There are adapters to go between different types, but otherwise they do not stick together.
I'll do a quick summation of my personal thoughts on each type. It's best if you can try some of each brand yourself, or at least investigate the ones that are of most interest. In the end, most people get whatever brand comes in the set they start with. ;-)
Scalextric: flexible, least expensive, small, slick surface great for a variety of grip levels depending on tyre type and prep, but mediocre electrical connections
Carrera: stiff, strong, expensive, BIG enough for 1/24, not as good for small spaces, good electrical connections, plus stainless steel rail, slightly less slick than Scalextric
Ninco: flexible, medium sized but with tight turns so can fit a lot in a small space, very rough surface for exceptional grip even with bad tires, excellent electrical connections, also expensive.
SCX: old type was like Scalextric original, new type works with their digital track. Flexible and small-ish size, rough but not too much surface texture, mediocre/good electrical, slightly more expensive than Scalextric
My personal ideal track doesn't exist. It would have the size/shape/surface of Scalextric Sport track, but the connections of Ninco track. Or I could say, Ninco track with a Scalextric Sport surface. Ninco also has the widest range of curve sizes, from the tight R1 to the extra wide R5. Carrera's R1 turns are about the same as an R2 in every other brand, because they're cars' long guide keels won't make it through tighter turns. But, Carrera's larger size does make it possible to run larger scale cars, and is often the choice for plastic track when a large area is available for it.
Then there's wood. If you're at all handy, and especially if you're not interested in digital (since that adds some work to the process), take a serious look at building a wood track. They're dead easy to do, cheap to make compared to the money for a big plastic track, and smooth as butter to drive on. The amount of grip you get is entirely up to you in choosing the paint application, and the continuity is outstanding since it's just one long rail, either copper tape of braid. Oldslotracer.com and other sites have tons of helpful info on make your own track.