So, two characters who're fantasy creatures that, despite not being human, are designed to be analogous to Black people, with one being handled well while the other...isn't.
Anyhow, I'd personally give this to Garnet. Since speed's been equalized and she'd just blitz Popo otherwise, Word of God states that she can casually survive being in the core of the Sun (
http://shikai-of-the-4th-world.tumblr.com/post/98609800488), which has killed other Dragon Ball villains who're definitely tougher than Popo. Additionally, since she's got limitless stamina so long as her gemstones aren't damaged and her gauntlets form around her hands to shield them, she's likely able to play the long game in hand-to-hand and wear Popo out if need be, as there's nothing to suggest that he can last as long as she can.
Admittedly, Popo could get on his carpet, teleporting around and away from Garnet and flinging Ki blasts at her the whole time (I'm thinking that one bit where Goku's teleporting around the Four Star Dragon in GT) but, well...
1. There's nothing to indicate that the carpet can teleport that much consistently or accurately.
2. Although it's introduced after this, implying that Toriyama likely just hadn't thought of it at the time, the fact that Popo doesn't offer Goku the carpet to get to Nappa and Raditz implies that it's not fit for combat situations.
3. Despite what his intelligence is listed as here, Popo doesn't seem smart enough to think of that since, in the original manga and Japanese dub at least, his dialogue's written in a rudimentary way to give the impression that he's uneducated.
4. Garnet has answers to that strategy; she can shapeshift her arms like she did against Pearl and Amethyst to negate any range issue, she could make shockwaves or fire her gauntlets to knock Popo out of the sky, or she could just block and dodge them long enough for Popo to tire himself out.
So yeah, my vote's going to Garnet on this one.