I'll add my two cents as an owner of both the JayBirds Blue Buds X and Beats Powerbeats 2. I needed something wireless for running and going to the gym and did a little research and went with the JayBirds a little over a year ago. I didn't even consider the Beats because....well, I wrote them off to being more of a fashion statement. The JayBirds sound great, but I constantly have an issue with them fitting properly, they come lose when I would run. I just don't love how they felt in my ears.
Enter the PowerBeats 2. My friend tipped me off to a Black Friday deal and suggested I grabbed them. He told me he had the same issues with Beats initially, but that all went away when he started using them. So I ordered the black pair (which looked the most subtle) and figured I'd try them out and at worse case, I could re-sell them if I ended up hating them. Well, I have to say these have been my go-to headphones ever since. I love the fit... just perfect and gives a great seal when active. These things never come out of my ears no matter what I'm doing. The attachments that come with the Beats help as I was able to find an even better fit by swapping the ear tips. After a while, I forget I'm even wearing them, while with the Blue Buds X, I was always aware.
Now, the bass is a little heavy on the Powerbeats 2, that's been said of all Beats headphones. I've never heard any other Beats product, so I can't compare how they are over their standard over the ear heahphones. But I felt like music on the Powebeats felt more punchier than the JayBirds, which focus more on mids to my ears. So I don't mind the slight bass push at all, it's not exaggerated. I also listen to a lot of podcasts, talk and video and they all sound great with the Powerbeats 2. In fact, I watch videos on my tablet when I'm on the treadmill... and with the Jaybirds, the audio/video sync seemed slightly off. But not with the Powerbeats 2, which kept the audio/video in sync (or maybe it was off slightly, just not enough to notice). The Powerbeats 2 are also louder than any other headphone I've used (wireless or wired) and I love that for the gym.
The battery time for both is about the same, I've never come close to losing power with either.
In my opinion, you can't go wrong with either one sound wise. But for comfort and perfect fit, it's the Powerbeats 2 for me. The Blue Buds X just can't compare in that arena and I haven't used them in months.