All other factors being equal what are the chances that a guest worker will head towards southern italy rather than germany or belgium

I don't know what "all other" factors could mean - since we don't know what factors have already been mentioned - but I assume that the pay and work conditions would be the same (those could be the "all other" here and the difference is Italy vs Germany/Belgium).

Generally, Italy is not a very likely destination for migrant workers, since it has recently been struggling economically. The payment, working conditions and work stability are likely to be better in Germany or Belgium, so if one can find a job, there, one is more likely to go to Germany or Belgium