In my opinion, both guys are on two different levels musically. They aren't completely pop albums, regardless of them being labelled pop. One Direction's Made in The A.M. is almost like a pop/funk/indie type where as Justin's Purpose is pop/hip-hop/electronic, which has the ability to be remixed into a song they can play in a club. You won't find that on One Direction's album.
You can tell the effort that was put forth into both of these albums, though I have to say, Justin took his time to come out with an album he is completely proud of, which is how the music industry should work. Now you're probably like, really, One Direction's music is always good, they're always proud of the music they put out. I don't disagree whatsoever, but for the past five years, they've been nonstop on the road. Those five years, I've been to every show they've had in my state or semi-close in other states, even getting to meet them during one of their tours.
Clearly they're taking time off now, but I hope their next album takes them a year or two to write, truly giving their all to provide the best album they possibly can. I get it; I hate waiting, too because I'm still buzzing off of Taylor Swift's 1989, which came out last year. She always waits two years to release a new album. So next October is likely to be a big one; well, let's cross our fingers.
Both One Direction's and Justin Bieber's albums are going to sell, and I'm sure they'll both do great. But there will be fans comparing the sales of each stating whose album has done better. At this point, who cares? Their albums are out, and they're beautiful music to our ears. Let's enjoy!