When Iggy Azalea dropped her new single "Trouble" featuring Jennifer Hudson, we couldn't help but recall Taylor Swift's classic bad boy track, "I Knew You Were Trouble." Whose "Trouble" song is your fave?

While we may never know who inspired Taylor Swift's "I Knew You Were Trouble" -- though rumors persist that it was Harry Styles -- the Red track is one of our all time faves from T. Swift. Despite the song's upbeat facade, the lyrics are decidedly heartfelt (of course -- it's Taylor Swift) with an edge of both hurt and anger. "I knew you were trouble when you walked in / Shame on me now," Taylor sings on the chorus. The guitar-heavy, pop-sounding song -- so different than anything T. Swift had ever released before -- was totally a precursor to 1989.

While Taylor Swift looked back at her bad boy with trepidation, Iggy Azalea is all about her felon-like fella in "Trouble." (To be fair, Jennifer Hudson is more on the Taylor Swift side of things.) "A little trouble only makes for a good time," Iggy raps, "So all the normal red flags be a good sign." While we relate a little more to J. Hud's chorus ("Don't you come here thinkin' you ballin' / Ain't down for it," she belts) we're kind of obsessed with the old-school vibe of Iggy's track. It's totally reminiscent of the '70s, but with a slick, modern twist. And yes, it does make us swoon for the bad boy -- just a little.

Whose "Trouble" song is your fave? Cast your vote for Taylor Swift or Iggy Azalea and Jennifer Hudson in the poll below!

Watch Taylor Swift's "I Knew You Were Trouble" Video

Watch Iggy Azalea and Jennifer Hudson's "Trouble" Video

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