Super Sentai is of course better but I can't help but say that Power Rangers is also equally good..sure the first season is cheesy but Season 3 has much story elements and other seasons of Power Rangers are better than their Japanese counterparts such as Lost Galaxy and In Space. Other Power rangers are equally as good as their Japan counterparts like Lightspeed rescue and GOGO V and Timeranger and Time Force.
Gekiranger and Boukenger are better than the american counterparts for good reasons. Mystic Force is nowhere as good as Magiranger but hey,just me. RPM is definitely much darker than its japanese counterpart and Shinkenger is better than Super Samurai for good reasons.
Turbo is meant to be Batman but with power rangers and is horrible due to the japanese version being more comedic.
I could go on about this but overall,Super Sentai and Power Rangers are just as good and there are no losers in the end,just winners...with exceptions of few seasons of Sentai and PR.