gubamyster has already provided sources here are some more. The pros and cons are easy to find with google and searches here at Free Republic. Depends upon what is meant by "primary beneficiaries?" Is that the problem?
BTW, www.cis.org has an About page and google can be used to establish their credibility. You will find them used by the mainstream media for example as well as conservative groups. google for, "Center for Immigration Studies".
Here is one source for stats. There are studies for most immigrant groups. This one is for immigrants from Mexico the group that's most numerous and talked about. The Center for Immigration Studies' report at
http://www.cis.org/articles/2001/mexico/mexico.pdf
"Even after welfare reform, welfare use among Mexican immigrant households remains much higher than that of natives. An estimated 33.9 percent of households headed by legal Mexican immigrants and 24.9 percent of those headed by illegal Mexican immigrants used at least one major welfare program. In contrast, 14.8 percent of native households used welfare. Moreover, Mexican immigrant welfare use remains much higher than that of natives, even among Mexican immigrants who have lived in the United States for many years (see Figure 1)." [end excerpt]
googling, immigrants welfare, turns up hundreds of thousands of hits. The above is one. Some other immigrant groups have similar stats. It's been discussed pro and con here in the past. google,
immigrants welfare site:www.freerepublic.com
Dave S, You referred to Congressman Tancredo as a bigot. Do you have sources that suggest that in fact he is a bigot? TIA.