I might get some debate on this, but I really don’t think many would quibble if I state that there is no bad modern scale rails, at least in HO…with which I am most familiar. It’s virtually all nickel-silver, and it all works. Treat it nicely, don’t abuse it, and it will all last a long time.
Brass and steel track are largely a thing of the past, and most would agree…good riddance. Maybe in other scales it is still useful, maybe even preferred, but not in the HO world with which I am familiar. So, take your pick…the section small pieces, some with fake plastic ballast (Atlas, Kato, Bachmann, others), or the flex type (Micro Engineering, Model Power, Peco, Atlas, Walthers, and a newcomer…I think Rapido).
It is usually not the track that gives you troubles. It might be tight curves or improper joins, but most often it is the switches, or what we call “turnouts” in the hobby. Too often they won’t play nicely with the rest of the track and cause derailments. Quality ones are made by Walthers/Shinohara, Peco, Atlas, and Micro Engineering, to name the most widely used ones. Even then, sometimes the flange path in the frog needs deepening or widening, or even narrowing, or the sharp sliding points rails won’t be sharp enough or lie tightly against their stock rails. When that happens, the wheel flanges might pick the point and cause a derailment.
I gave you more than you asked, but that should help…hopefully. My advice is to stick with nickel-silver, even if you can get it second-hand.