Poker Sites Random Number Generators

Do you think all sites use RNG to determine the cards? If they do are they all the same? I have noticed some sites that the best preflop hand rarely wins. I have also been playing 2 tables and had the same hole cards and flop come down at the same time.

Which site do you think has the best RNG? Is it possible that UB programs their cards to encourage action by not being random? It seems that way to me but my experience would be to small of a sample to be correct.