best type of track

[Jhanecker2]

the only problem with dissimilar materials would be the difference between the electrochemical potential differences of the materials. the size differences of the rail Code is immaterial.

[James in FL]

If one would choose to use both Steel and Nickel Silver rails, on the same layout, I would recommend they were connected with an isolating (plastic) joiner.
Even without soldering them together, and using regular joiner, there would still be an electrochemical reaction at the joint. In time, conductivity between the two types will fail.

[Joe Satnik]

I'd doubt that the steel track has steel rail joiners. 

Most likely they're nickel-silver.

Joe Satnik

[Jhanecker2]

Since there are no seperate rail joiners manufactured for N/s , steel or brass tracks  that I know of , at least in HO scale , I think you are correct.  I remember from other posts that steel rails have a Zinc coating . From observation I know that Lock-Trak has Copper connection strips.  If you keep the track clean it should work reasonably well electrically , not perfectly.  But what does ?