Do you think in Polish majority minds exist some principal difference between Catholic and Orthodox Christianity?
In Polish majority minds some principal difference doesn`t exist. Simply speaking, most people who are Catholic here don`t care about Orthodox/Greek Christainity because they have no real contact with each other. As I suggested in my post before, combined Catholic and Orthodox people occupy outback regions of the country and they constitute more or less less than 1% of the society.
Do Poles believe that Catholic or Protestant denominations are superior to Orthodoxy?
Yes, they sort of do, naturally, because Roman Catholic denomination is prevalent in Poland. Check google for statistics.