Not often. Certainly it's true that Soviets who did make it to the west were surprised by material abundance. Leon Aron's biography of Boris Yeltsin talks about how shattering it was for Yeltsin to see an ordinary Texas supermarket. Keep in mind that Yeltsin had been a member of the Soviet elite--a member of the Politburo--and didn't get that chance until 1989.

That said, the nature of Soviet society is such that those who did make it to the west--diplomats, athletes, artists, scientists--would talk about it and their stories would be repeated to a much larger number of people.

Is this vast disparity in food quantity and variety between the USSR and The West actually demonstrably true?

Some time ago i discovered this archived publication by a professor at Maine, Joseph Medley. http://web.archive.org/web/20070314063045/http://www.usm.maine.edu/eco/joe/works/Soviet.html

It deals with what he calls the myths of Soviet agriculture and its alleged inefficiency. Summarily, he deals with common criticisms aimed at the Soviet System and - at least purports to - correct them.

For example he does not believe that the Soviet System was chronically inefficient. The shortages, in his view, were the result of wage increases and government subsidy on consumption which led to very low meat prices for the consumer.

Critics contend that the Soviet Union has been plagued by increasing shortages of meat, even while the government provides massive subsidies, overburdens its budget and, consequently, creates inflation. The Soviet government does provide large subsidies for consumption of meat (and dairy) products (Koopman 1990:4). The large consumption subsidy strains the Union budget. However, the problem is not that socialist agriculture has failed to produce meat, or that the Soviet population is going hungry. As shown in the last section, meat production increased in the 1980's. Yet in 1965 there were surpluses, while today there are shortages.

In his tables he also notes that caloric consumption in the USSR was virtually the same as in America (following data is from the late 60's).

UNITED STATES 3,200 3.39

WEST GERMANY 2,960 2.86

BRITAIN 3,150 3.10

USSR 3,180 3.24

Lastly, he points out that the overall percentage of meat, vegetables and fruit in the Soviet diet increased over time at the expense grain and potato consumption. As such the quality of the diet increased. He even states that meat consumption in the USSR, at times, was higher than in Italy and Norway (its at the bottom of the article with the other tables)

I apologize for the heavy use of quotation, but let me quote part of his conclusion:

The myth created about Soviet agriculture is pernicious because it supports seemingly non-ideological policy interpretations and alternatives. In isolation each contention by Western critics seems reasonable, despite some exaggeration and inattention to conflicting evidence. However, taken all together they form a chorus singing the praises of one system while damning another. The net effect is to create a mythology of capitalist rationality and efficiency that contrasts favorably with the exaggerated weaknesses of the Soviet agricultural system. The possibility that socialized agriculture may be able to make valuable contributions to improving human welfare should not be dismissed on the basis of this myth.

I'd like to point out that i have no understanding of Soviet History, its economy or whether or not the above can be taken at face value. I'd really like if someone specialized in the USSR could make a comment on this.