While Jenner sported the jumpsuit first, we have it give it to J.Lo -- who manages to look half her age no matter what she's wearing!
Plus, we have a feeling there won't be any bad blood between these two. "Jenny from the Block" rang in the big 4-7 with Jenner's sister, Kim Kardashian, by her side.
Kardashian celebrated with Lopez at her big birthday bash, hosted by Benny Medina and Caspar Smart, in Las Vegas -- but she wasn't alone. Calvin Harris was also on hand for the big event, posing with Lopez, Kim and Khloe Kardashian’s ex, French Montana.