A lot of it comes down to preference. The cheapest track by far is tubular track, while Lionel no longer makes it, Menards seems to have taken up the charge with that, and for switches Ross makes a ton of different styles, tinplate style to scale. Tubular can run almost anything (deep flanges have no problems on it), but also can take a lot of work to look more realistic (ballasting, putting extra ties in it, painting the rails).
For me Gargraves rail and Ross Switches is a kind of jolly median, though Gargraves disturbs some because the ties are larger than scale and isn't quite protypical, for price and performance to me it is in a sweet spot (and that is me).
Atlas makes nice track, but even with a discount it will be more expensive, and as others have pointed out, it can be difficult to get, Atlas had horrendous problems with shipping (Gargraves is made in Upstate NY, Ross is in Connecticut) for a while, and still can have problems, plus the variety ross offers with switches is much, much larger than Atlas. Atlas looks nice, though, and the nickel silver rail is easier to maintain (won't work with magnetraction is you wanted to use engines with that).
MTH scale trax to me is the best looking, most prototypical, but it is expensive, it can be tricky to work with, and can have availability issues.
Scale Trax and Atlas track also has a drawback if you run older tinplate equipment I hear, some of the deep flanged engines and rolling stock may have trouble with those (least that is what I have heard, haven't tried doing that myself).
Some people work with Lionel fast track or the plastic bodied track that MTH and Atlas produce (it is track integrated with a plastic roadbed) and make it look quite nice. Because of the plastic, these tend to be a lot noisier, though, and can take some work to deaden that sound. They also limit what you can do with them, for example cutting. Another factor is they aren't particularly cheap, either.
In the end it comes down to what you can affford which in turn involves how realistic you want it, how big the layout is (the differences in price become a lot bigger the larger the layout), and what looks good to you, all have their pluses and minuses. If you are on a budget, you can buy tinplate track really cheaply used, and 'fix it up' with extra ties, ballast and such, and it can look pretty darn good (with Ross Switches, Lionel tinplate switches are pretty rugged, but don't look as good IMO). There is no one right way,no really 'best' product, really depends on your unique needs and limits, too.