Better quality TVs had three IF stages (like my Dumont RA-103), or even four (like my RCA CT-100). More IF stages means more amplification of the incoming signal, resulting in greater sensitivity (ability to pull in weak, far-away stations). A TV with only two IF stages would only have worked well in a metro area with nearby stations.
Sensitivity
per se is not such a big deal nowadays, when many collectors feed their restored TVs from a DVD player or whatnot, with a nice strong signal. The number of IF stages can be interpreted as a sign of overall quality, however. If the manufacturer skimped in that area, they may have skimped in others, too.
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html